{
  "paper": {
    "school": "Anglo-Chinese School (Primary)",
    "year": 2022,
    "level": "P4",
    "label": "Semestral Assessment 2",
    "source_prefix": "ACS 2022 P4 Semestral Assessment 2",
    "has_answer_key": true
  },
  "questions": [
    {
      "n": 1,
      "type_id": 1,
      "question": "In the number 71 059, which digit is in the thousands place?",
      "answer0": "1",
      "answer1": "5",
      "answer2": "7",
      "answer3": "9",
      "correct_answer": 0,
      "skill_id": 105,
      "difficulty_id": 1,
      "explanation": "Place values of 71 059: 7 = ten thousands, 1 = thousands, 0 = hundreds, 5 = tens, 9 = ones. The thousands digit is 1.",
      "hints": ["Write out the place value of each digit from right to left: ones, tens, hundreds, thousands.", "The thousands place is the fourth digit from the right."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q1",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 1."
    },
    {
      "n": 2,
      "type_id": 1,
      "question": "29 056 rounded to the nearest hundred is [?].",
      "answer0": "29 000",
      "answer1": "29 060",
      "answer2": "29 100",
      "answer3": "30 000",
      "correct_answer": 2,
      "skill_id": 109,
      "difficulty_id": 1,
      "explanation": "Look at the tens digit (5). Since 5 rounds up, 29 056 rounds to 29 100.",
      "hints": ["To round to the nearest hundred, look at the tens digit.", "If the tens digit is 5 or more, round the hundreds up."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q2",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 3 (29 100)."
    },
    {
      "n": 3,
      "type_id": 1,
      "question": "What is the sum of 53.08 and 1.7?",
      "answer0": "51.38",
      "answer1": "53.25",
      "answer2": "54.15",
      "answer3": "54.78",
      "correct_answer": 3,
      "skill_id": 129,
      "difficulty_id": 1,
      "explanation": "Align decimal points: 53.08 + 1.70 = 54.78.",
      "hints": ["Line up the decimal points before adding.", "Write 1.7 as 1.70 so both numbers have two decimal places."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q3",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 4 (54.78)."
    },
    {
      "n": 4,
      "type_id": 1,
      "question": "Which one of the following decimals is the greatest?",
      "answer0": "0.103",
      "answer1": "0.095",
      "answer2": "0.231",
      "answer3": "0.052",
      "correct_answer": 2,
      "skill_id": 124,
      "difficulty_id": 1,
      "explanation": "Compare the tenths digit first: 0.231 has 2 tenths, the largest. So 0.231 is greatest.",
      "hints": ["Compare the digits in the tenths place first.", "The decimal with the largest tenths digit is the greatest."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q4",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 3 (0.231)."
    },
    {
      "n": 5,
      "type_id": 1,
      "question": "Which of the following is 5 tens, 28 tenths and 9 thousandths in numerals?",
      "answer0": "50.289",
      "answer1": "50.298",
      "answer2": "52.089",
      "answer3": "52.809",
      "correct_answer": 3,
      "skill_id": 123,
      "difficulty_id": 2,
      "explanation": "5 tens = 50. 28 tenths = 2.8. 9 thousandths = 0.009. Total = 50 + 2.8 + 0.009 = 52.809.",
      "hints": ["28 tenths equals 2.8, not 0.28.", "Add 50 + 2.8 + 0.009."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q5",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 4 (52.809)."
    },
    {
      "n": 6,
      "type_id": 1,
      "question": "Mary has some beads. Lina has 3 times as many beads as Mary. The two girls have 2100 altogether. How many beads does Lina have?",
      "answer0": "525",
      "answer1": "700",
      "answer2": "1050",
      "answer3": "1575",
      "correct_answer": 3,
      "skill_id": 118,
      "difficulty_id": 2,
      "explanation": "Mary = 1 unit, Lina = 3 units, total = 4 units = 2100. 1 unit = 525. Lina = 3 x 525 = 1575.",
      "hints": ["Let Mary be 1 unit; Lina is 3 units, so there are 4 units in total.", "Divide 2100 by 4, then multiply by 3 for Lina."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q6",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 4 (1575)."
    },
    {
      "n": 7,
      "type_id": 1,
      "question": "The figure is made up identical triangles. What fraction of the figure is shaded?",
      "answer0": "1/2",
      "answer1": "1/3",
      "answer2": "2/3",
      "answer3": "3/8",
      "correct_answer": 1,
      "skill_id": 120,
      "difficulty_id": 2,
      "explanation": "There are 6 identical triangles in total and 2 are shaded, so the shaded fraction is 2/6 = 1/3.",
      "hints": ["Count the total number of identical triangles.", "Count how many are shaded, then simplify the fraction."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q7",
      "image_needed": true,
      "image_options": false,
      "image_file": "q7.png",
      "image_page": 4,
      "image_bbox": [0.33, 0.16, 0.55, 0.31],
      "image_loc": "upper area of page, below the question stem — arrangement of triangles with two shaded",
      "notes": "Key: option 2 (1/3). 6 triangles, 2 shaded."
    },
    {
      "n": 8,
      "type_id": 1,
      "question": "Find the value of 7/9 - 2/3.",
      "answer0": "1/9",
      "answer1": "5/6",
      "answer2": "3/4",
      "answer3": "5/9",
      "correct_answer": 0,
      "skill_id": 121,
      "difficulty_id": 1,
      "explanation": "Convert 2/3 to ninths: 2/3 = 6/9. Then 7/9 - 6/9 = 1/9.",
      "hints": ["Make the denominators the same: 2/3 = 6/9.", "Subtract the numerators once denominators match."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q8",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 1 (1/9)."
    },
    {
      "n": 9,
      "type_id": 1,
      "question": "Ken came out of the MRT station and faced the coffee shop. He made a 225 degree clockwise turn followed by a 90 degree anticlockwise turn. Which direction did he face in the end?",
      "answer0": "Mall",
      "answer1": "Church",
      "answer2": "Playground",
      "answer3": "Supermarket",
      "correct_answer": 1,
      "skill_id": 452,
      "difficulty_id": 3,
      "explanation": "Net turn = 225 degrees clockwise - 90 degrees = 135 degrees clockwise. Coffee shop is at SE. Turning 135 degrees clockwise from SE (each 45 degrees is one compass point) lands on W, which is the Church. Answer: Church.",
      "hints": ["A clockwise turn followed by an anticlockwise turn: subtract to get the net clockwise turn (135 degrees).", "Each adjacent labelled direction is 45 degrees apart; count 3 steps clockwise from Coffee shop."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q9",
      "image_needed": true,
      "image_options": false,
      "image_file": "q9.png",
      "image_page": 5,
      "image_bbox": [0.21, 0.19, 0.72, 0.4],
      "image_loc": "middle of page — 8-point compass diagram with MRT Station centre and labelled directions, plus North arrow on the right",
      "notes": "Key: option 2 (Church)."
    },
    {
      "n": 10,
      "type_id": 1,
      "question": "Ken bought 5 kg of sugar. He used 0.36 kg of the sugar to make a cake and packed the rest equally into 8 packets. How much did each packet of sugar weigh?",
      "answer0": "0.58 kg",
      "answer1": "0.625 kg",
      "answer2": "2.88 kg",
      "answer3": "4.64 kg",
      "correct_answer": 0,
      "skill_id": 131,
      "difficulty_id": 2,
      "explanation": "Remaining sugar = 5 - 0.36 = 4.64 kg. Each packet = 4.64 / 8 = 0.58 kg.",
      "hints": ["First subtract the 0.36 kg used for the cake.", "Divide the remaining mass by 8 packets."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q10",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 1 (0.58 kg)."
    },
    {
      "n": 11,
      "type_id": 1,
      "question": "Which of the following statement is correct?",
      "answer0": "Angle XYS is 60 degrees.",
      "answer1": "Angle XYZ is an acute angle.",
      "answer2": "Angle SYR is a right angle.",
      "answer3": "The sum of angle SYR and angle RYZ is 170 degrees.",
      "correct_answer": 2,
      "skill_id": 140,
      "difficulty_id": 3,
      "explanation": "Reading the protractor: XYZ is a straight line (180 degrees), so option 2 is wrong. Angle SYR is 90 degrees (a right angle) — option 3 is correct. XYS measures 120 degrees not 60, and the sum in option 4 does not equal 170.",
      "hints": ["XYZ lies along the protractor base, so it is a straight line.", "Read the scale carefully to identify which angle equals 90 degrees."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q11",
      "image_needed": true,
      "image_options": false,
      "image_file": "q11.png",
      "image_page": 6,
      "image_bbox": [0.28, 0.15, 0.72, 0.33],
      "image_loc": "upper-middle of page — protractor with rays labelled S, R, X, Z and centre Y",
      "notes": "Key: option 3 (angle SYR is a right angle)."
    },
    {
      "n": 12,
      "type_id": 1,
      "question": "A number is between 20 and 40. It is a multiple of 3. When it is divided by 7, there is a remainder of 1. What is the number?",
      "answer0": "39",
      "answer1": "36",
      "answer2": "24",
      "answer3": "21",
      "correct_answer": 1,
      "skill_id": 114,
      "difficulty_id": 2,
      "explanation": "Multiples of 3 between 20 and 40: 21, 24, 27, 30, 33, 36, 39. Check division by 7 with remainder 1: 36 / 7 = 5 r 1. So the number is 36.",
      "hints": ["List the multiples of 3 between 20 and 40.", "Which of them gives remainder 1 when divided by 7? (i.e. is one more than a multiple of 7)"],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q12",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: option 2 (36)."
    },
    {
      "n": 13,
      "type_id": 1,
      "question": "Which of the following is symmetrical?",
      "answer0": "Shape 1 (parallelogram)",
      "answer1": "Shape 2 (wavy flag)",
      "answer2": "Shape 3 (regular pentagon)",
      "answer3": "Shape 4 (octagon)",
      "correct_answer": 2,
      "skill_id": 144,
      "difficulty_id": 2,
      "explanation": "A regular pentagon has lines of symmetry, so it is symmetrical. The parallelogram and wavy flag are not line-symmetric. Answer: Shape 3.",
      "hints": ["A figure is symmetrical if it can be folded so both halves match exactly.", "Check each shape for a mirror line."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q13",
      "image_needed": true,
      "image_options": true,
      "image_file": null,
      "image_page": 7,
      "image_bbox": [0.22, 0.14, 0.5, 0.62],
      "image_loc": "options stacked down the left of the page: (1) parallelogram, (2) wavy flag, (3) pentagon, (4) octagon — crop each option separately",
      "notes": "Key: option 3 (pentagon). image_options true — crop q13_opt0..3.png for the four shapes."
    },
    {
      "n": 14,
      "type_id": 1,
      "question": "In the grid, Raju is standing at point P facing north-west. Then, he makes a 3/4 turn in a clockwise direction. At which point does he face now?",
      "answer0": "Q",
      "answer1": "T",
      "answer2": "R",
      "answer3": "S",
      "correct_answer": 1,
      "skill_id": 451,
      "difficulty_id": 3,
      "explanation": "A 3/4 turn clockwise = 270 degrees. Starting facing north-west and turning 270 degrees clockwise ends facing south-west. From P, the south-west direction points to T. Answer: T.",
      "hints": ["A 3/4 turn is 270 degrees.", "Starting from NW, turn 270 degrees clockwise (NW to NE to SE to SW) to find the new facing direction, then read the grid."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q14",
      "image_needed": true,
      "image_options": false,
      "image_file": "q14.png",
      "image_page": 8,
      "image_bbox": [0.26, 0.19, 0.7, 0.43],
      "image_loc": "middle of page — square grid with points P (centre), S, Q, R, T marked, North arrow at right",
      "notes": "Key: option 2 (T)."
    },
    {
      "n": 15,
      "type_id": 1,
      "question": "The figure shows a rectangle of sides 27 cm by 14 cm and a square of sides 8 cm. Find the area of the shaded part of the figure.",
      "answer0": "314 cm2",
      "answer1": "330 cm2",
      "answer2": "346 cm2",
      "answer3": "442 cm2",
      "correct_answer": 0,
      "skill_id": 138,
      "difficulty_id": 2,
      "explanation": "Rectangle area = 27 x 14 = 378 cm2. The unshaded square = 8 x 8 = 64 cm2. Shaded = 378 - 64 = 314 cm2.",
      "hints": ["Find the whole rectangle's area first.", "Subtract the area of the unshaded square."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q15",
      "image_needed": true,
      "image_options": false,
      "image_file": "q15.png",
      "image_page": 9,
      "image_bbox": [0.24, 0.17, 0.74, 0.36],
      "image_loc": "upper-middle of page — shaded rectangle (27 cm wide, 14 cm tall) with an unshaded square cut from the top-left corner",
      "notes": "Key: option 1 (314 cm2)."
    },
    {
      "n": 16,
      "type_id": 2,
      "question": "Write seventy-three thousand and twelve in figures.",
      "answer0": "73012",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 106,
      "difficulty_id": 1,
      "explanation": "Seventy-three thousand = 73 000. Twelve = 12. Together: 73 012.",
      "hints": ["Seventy-three thousand is 73 000.", "Add the twelve at the end: 73 012."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q16",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 7302 in the answer sheet appears to be a typo; correct value is 73012 (seventy-three thousand and twelve)."
    },
    {
      "n": 17,
      "type_id": 2,
      "question": "Arrange the following numbers from the smallest to the greatest.\n2810 , 2081 , 2108",
      "answer0": "2081",
      "answer1": "2108",
      "answer2": "2810",
      "answer3": null,
      "correct_answer": null,
      "skill_id": 107,
      "difficulty_id": 1,
      "explanation": "Compare by place value: 2081 < 2108 < 2810. Smallest to greatest: 2081, 2108, 2810.",
      "hints": ["Compare the hundreds digit after the thousands digit.", "Order them from least to greatest."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q17",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 2081, 2108, 2810."
    },
    {
      "n": 18,
      "type_id": 2,
      "question": "What is the missing number in the box?\n0.42 = 42/[?]",
      "answer0": "100",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 126,
      "difficulty_id": 1,
      "explanation": "0.42 = 42 hundredths = 42/100, so the missing denominator is 100.",
      "hints": ["0.42 means 42 hundredths.", "Hundredths means the denominator is 100."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q18",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 100. Figure is just the equation 0.42 = 42/[box]; no separate diagram needed."
    },
    {
      "n": 19,
      "type_id": 2,
      "question": "Find the product of 67 and 898.",
      "answer0": "60166",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 116,
      "difficulty_id": 2,
      "explanation": "67 x 898 = 67 x 900 - 67 x 2 = 60 300 - 134 = 60 166.",
      "hints": ["Multiply 67 by 898 using the standard algorithm.", "Or compute 67 x 900 then subtract 67 x 2."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q19",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 67 x 898 = 60166."
    },
    {
      "n": 20,
      "type_id": 2,
      "question": "Find the common factors of 16 and 40.",
      "answer0": "1",
      "answer1": "2",
      "answer2": "4",
      "answer3": "8",
      "correct_answer": null,
      "skill_id": 113,
      "difficulty_id": 2,
      "explanation": "Factors of 16: 1, 2, 4, 8, 16. Factors of 40: 1, 2, 4, 5, 8, 10, 20, 40. Common factors: 1, 2, 4, 8.",
      "hints": ["List all factors of each number.", "Pick the factors that appear in both lists."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q20",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 1, 2, 4, 8 (four common factors as a sequence)."
    },
    {
      "n": 21,
      "type_id": 2,
      "question": "Write 45/7 as a mixed number.",
      "answer0": "6 3/7",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 119,
      "difficulty_id": 1,
      "explanation": "45 / 7 = 6 remainder 3, so 45/7 = 6 3/7.",
      "hints": ["Divide 45 by 7 to find the whole number part.", "The remainder over 7 is the fraction part."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q21",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 6 3/7."
    },
    {
      "n": 22,
      "type_id": 2,
      "question": "The table shows the number of students in the different CCAs from Primary 4M. What is the difference between the CCA with the greatest number of students and the least number of students?",
      "answer0": "12",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 148,
      "difficulty_id": 1,
      "explanation": "Greatest = Robotics Club (17), least = Environmental Club (5). Difference = 17 - 5 = 12.",
      "hints": ["Find the largest and smallest values in the table.", "Subtract the smallest from the largest."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q22",
      "image_needed": true,
      "image_options": false,
      "image_file": "q22.png",
      "image_page": 14,
      "image_bbox": [0.14, 0.34, 0.86, 0.47],
      "image_loc": "middle of page — CCA table (Environmental Club 5, Robotics Club 17, Floorball 11, Basketball 9); shared with Q23",
      "notes": "Key: 17 - 5 = 12."
    },
    {
      "n": 23,
      "type_id": 2,
      "question": "What fraction of the students in Primary 4M are in the basketball CCA? (Give your answer in the simplest form.)",
      "answer0": "3/14",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 120,
      "difficulty_id": 2,
      "explanation": "Total students = 5 + 17 + 11 + 9 = 42. Basketball = 9. Fraction = 9/42 = 3/14.",
      "hints": ["Add up all the students to get the total.", "Write basketball over the total, then simplify."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q23",
      "image_needed": true,
      "image_options": false,
      "image_file": "q23.png",
      "image_page": 14,
      "image_bbox": [0.14, 0.34, 0.86, 0.47],
      "image_loc": "middle of page — same CCA table as Q22",
      "notes": "Key: 5+17+11+9=42; 9/42 = 3/14. Refers to the table shared with Q22."
    },
    {
      "n": 24,
      "type_id": 2,
      "question": "In the figure shown, PQRS is a square. Find angle URT.",
      "answer0": "14",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 139,
      "difficulty_id": 3,
      "explanation": "Angle SRQ = 90 degrees (square corner at R). Angle SRT = 41 degrees and angle TRU = 35 degrees are part of it; URQ = 35 degrees? Using the key: 35 + 41 = 76, then 90 - 76 = 14. Angle URT = 14 degrees.",
      "hints": ["The corner angle of the square at R is 90 degrees.", "Subtract the two marked angles (35 degrees and 41 degrees) from 90 degrees."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q24",
      "image_needed": true,
      "image_options": false,
      "image_file": "q24.png",
      "image_page": 15,
      "image_bbox": [0.29, 0.14, 0.57, 0.33],
      "image_loc": "upper-left of page — square PQRS with vertices labelled, lines from R to U and T, marked angles 35 degrees and 41 degrees at R",
      "notes": "Key: 35 + 41 = 76; 90 - 76 = 14. Angle URT = 14 degrees."
    },
    {
      "n": 25,
      "type_id": 0,
      "question": "Measure and write down the size of angle x.",
      "answer0": null,
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 140,
      "difficulty_id": 2,
      "explanation": "Using a protractor, measure the angle between the two rays at the marked vertex. The key gives 37 degrees.",
      "hints": ["Place the protractor centre on the vertex of angle x.", "Align the base line with one ray and read the scale at the other ray."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q25",
      "image_needed": true,
      "image_options": false,
      "image_file": "q25.png",
      "image_page": 15,
      "image_bbox": [0.35, 0.43, 0.75, 0.65],
      "image_loc": "middle of page — an acute angle drawn with a horizontal ray and a slanting ray meeting at the right, angle marked x",
      "notes": "Key answer: 37 degrees. type_id 0 — requires physically measuring the printed angle with a protractor, no definite value derivable from text. SKIPPED on insert."
    },
    {
      "n": 26,
      "type_id": 2,
      "question": "Arrange the following fractions from the smallest to the greatest.\n2/5 , 7/10 , 1/4",
      "answer0": "1/4",
      "answer1": "2/5",
      "answer2": "7/10",
      "answer3": null,
      "correct_answer": null,
      "skill_id": 121,
      "difficulty_id": 2,
      "explanation": "Convert to twentieths: 2/5 = 8/20, 7/10 = 14/20, 1/4 = 5/20. Order: 5/20 < 8/20 < 14/20, i.e. 1/4, 2/5, 7/10.",
      "hints": ["Use a common denominator such as 20.", "Compare the numerators once the denominators match."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q26",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 1/4, 2/5, 7/10 (smallest to greatest)."
    },
    {
      "n": 27,
      "type_id": 2,
      "question": "There are some chocolates in a box. The chocolates can be shared equally among 6 children or 8 children. What is the smallest possible number of chocolates in the box?",
      "answer0": "24",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 115,
      "difficulty_id": 2,
      "explanation": "The smallest number divisible by both 6 and 8 is the LCM. Multiples of 8: 8, 16, 24; 24 is also a multiple of 6. So LCM(6, 8) = 24.",
      "hints": ["Find the lowest common multiple of 6 and 8.", "List multiples of 8 and find the first one that is also a multiple of 6."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q27",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 24."
    },
    {
      "n": 28,
      "type_id": 2,
      "question": "Linda took 1 h 45 min to complete a practice paper. She finished the practice paper at 3.20 p.m. At what time did she start doing the practice paper? Express your answer in 24-hour clock.",
      "answer0": "1335",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 135,
      "difficulty_id": 2,
      "explanation": "3.20 p.m. = 1520 in 24-hour clock. Subtract 1 h 45 min: 1520 - 1 h = 1420, then - 45 min = 1335. Start time = 1335.",
      "hints": ["Convert 3.20 p.m. to 24-hour time (1520).", "Subtract 1 h 45 min from 1520."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q28",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 1335 Hrs."
    },
    {
      "n": 29,
      "type_id": 2,
      "question": "Round 89.895 to the nearest hundredth.",
      "answer0": "89.90",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 128,
      "difficulty_id": 2,
      "explanation": "The hundredths digit is 9 and the thousandths digit is 5, so round up: 89.895 rounds to 89.90.",
      "hints": ["To round to the nearest hundredth, look at the thousandths digit.", "Since the thousandths digit is 5, round the hundredths up."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q29",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 89.90."
    },
    {
      "n": 30,
      "type_id": 2,
      "question": "The figure is made up of 3 identical squares and 1 rectangle. The area of a square is 16 cm2. Find the area of the figure.",
      "answer0": "108",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 138,
      "difficulty_id": 3,
      "explanation": "Square side = 4 cm (since 4 x 4 = 16). The figure is 9 cm wide. The rectangle width = 9 - 4 = 5 cm and its height = 3 squares stacked = 3 x 4 = 12 cm, so rectangle = 5 x 12 = 60 cm2. Three squares = 3 x 16 = 48 cm2. Total = 60 + 48 = 108 cm2.",
      "hints": ["A square of area 16 cm2 has side 4 cm.", "The whole figure is 9 cm wide and 12 cm tall; split it into the 3 squares (right column) and the tall rectangle (left)."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q30",
      "image_needed": true,
      "image_options": false,
      "image_file": "q30.png",
      "image_page": 18,
      "image_bbox": [0.18, 0.18, 0.4, 0.36],
      "image_loc": "upper-left of page — figure of 3 stacked squares (right) and a tall rectangle (left), total width labelled 9 cm",
      "notes": "Key: 108 cm2."
    },
    {
      "n": 31,
      "type_id": 0,
      "question": "Complete the following symmetrical figure with AB as the line of symmetry.",
      "answer0": null,
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 145,
      "difficulty_id": 2,
      "explanation": "Reflect every line of the given half across line AB (the horizontal mirror line) to draw the mirror image below AB, completing the symmetrical figure.",
      "hints": ["Each point's reflection is the same perpendicular distance on the other side of AB.", "Reflect every vertex and join them in the same order."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q31",
      "image_needed": true,
      "image_options": false,
      "image_file": "q31.png",
      "image_page": 18,
      "image_bbox": [0.28, 0.55, 0.72, 0.78],
      "image_loc": "lower-middle of page — grid with a partial figure above horizontal line AB to be reflected",
      "notes": "type_id 0 — a draw/complete-the-figure task with no value/sequence answer. SKIPPED on insert. Answer key shows the completed reflected figure."
    },
    {
      "n": 32,
      "type_id": 2,
      "question": "The figure is made up of rectangle ABCD and square BEFC. The area of rectangle ABCD is 54 cm2 and EF = 6 cm. Find the perimeter of the figure.",
      "answer0": "42",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 136,
      "difficulty_id": 3,
      "explanation": "Square BEFC has side EF = 6 cm, so BC = 6 cm. Rectangle ABCD area = 54 cm2, so AB = 54 / 6 = 9 cm. The combined figure is a rectangle of length 9 + 6 = 15 cm and width 6 cm. Perimeter = 2 x (15 + 6) = 2 x 21 = 42 cm.",
      "hints": ["The square's side equals EF = 6 cm, which is also the width of the whole figure.", "Find AB from the rectangle's area, then the figure is one long rectangle; use perimeter = 2 x (length + width)."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q32",
      "image_needed": true,
      "image_options": false,
      "image_file": "q32.png",
      "image_page": 19,
      "image_bbox": [0.29, 0.18, 0.66, 0.31],
      "image_loc": "upper-middle of page — rectangle ABCD joined to square BEFC, height marked 6 cm; vertices A, B, E (top) and D, C, F (bottom)",
      "notes": "Key: 54/6=9, 15x2=30, 6x2=12, 30+12=42. Perimeter = 42 cm."
    },
    {
      "n": 33,
      "type_id": 2,
      "question": "The table shows the number of each type of buns Mr Tan sold in a day. Mr Tan sold three times as many chicken floss buns as curry potato buns. How many buns did he sell in total?",
      "answer0": "103",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 148,
      "difficulty_id": 2,
      "explanation": "Chicken floss = 42 = 3 x curry potato, so curry potato = 42 / 3 = 14. Total = 14 + 42 + 27 + 20 = 103 buns. (Red Bean = 27, Tuna = 20.)",
      "hints": ["Find curry potato buns: chicken floss is 3 times curry potato, so divide 42 by 3.", "Add all four types: chicken floss, red bean, curry potato and tuna."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q33",
      "image_needed": true,
      "image_options": false,
      "image_file": "q33.png",
      "image_page": 19,
      "image_bbox": [0.2, 0.5, 0.86, 0.58],
      "image_loc": "middle of page — bun sales table (Chicken floss 42, Red Bean 27, Curry Potato ?, Tuna 20, Total ?)",
      "notes": "Key: 42/3=14 curry potato; 14+42+27+20=103."
    },
    {
      "n": 34,
      "type_id": 2,
      "question": "The bar graph shows the number of patients who visited ABC Clinic over a period of 5 weeks. How many more patients visited ABC Clinic in Week 2 than in Week 5?",
      "answer0": "100",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 148,
      "difficulty_id": 1,
      "explanation": "Week 2 = 125? From the graph Week 2 = 175 and Week 5 = 75. Key gives 125 - 25 = 100; reading the bars, the difference is 100 patients.",
      "hints": ["Read the height of the Week 2 and Week 5 bars from the graph.", "Subtract Week 5 from Week 2."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q34",
      "image_needed": true,
      "image_options": false,
      "image_file": "q34.png",
      "image_page": 20,
      "image_bbox": [0.13, 0.16, 0.9, 0.45],
      "image_loc": "upper area of page — bar graph 'Patients who visited ABC Clinic' with bars for Weeks 1 to 5; shared with Q35",
      "notes": "Key: 125 - 25 = 100. Difference = 100 patients."
    },
    {
      "n": 35,
      "type_id": 2,
      "question": "All the patients who visited ABC Clinic in Week 3 took a vaccination. Each of them paid $18 for it. How much money was collected from all the patients in Week 3?",
      "answer0": "2250",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 148,
      "difficulty_id": 2,
      "explanation": "Week 3 patients = 125 (from the graph). Money collected = 125 x $18 = $2250.",
      "hints": ["Read the number of patients in Week 3 from the graph (125).", "Multiply the number of patients by $18."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q35",
      "image_needed": true,
      "image_options": false,
      "image_file": "q35.png",
      "image_page": 20,
      "image_bbox": [0.13, 0.16, 0.9, 0.45],
      "image_loc": "upper area of page — same bar graph as Q34",
      "notes": "Key: 125 x 18 = 2250. Answer $2250 (answer field prefixed with $)."
    },
    {
      "n": 36,
      "type_id": 2,
      "question": "Mason has $740 and Amin has $198. How much money must Mason give to Amin so that both of them have the same amount of money?",
      "answer0": "271",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 118,
      "difficulty_id": 2,
      "explanation": "Difference = $740 - $198 = $542. To equalise, Mason gives away half the difference: $542 / 2 = $271.",
      "hints": ["Find the difference between their amounts.", "Mason transfers half of that difference."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q36",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 740-198=542; 542/2=271. Answer $271. [3 marks]"
    },
    {
      "n": 37,
      "type_id": 2,
      "question": "A bottle which was completely filled with water weighed 2100 g. After 2/3 of the water was poured away, the bottle with the remaining water weighed 800 g. What was the mass of the empty bottle in grams?",
      "answer0": "150",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 122,
      "difficulty_id": 3,
      "explanation": "Water poured away = 2100 - 800 = 1300 g, which is 2/3 of the water. So 1/3 of water = 1300 / 2 = 650 g, and full water = 650 x 3 = 1950 g. Empty bottle = 2100 - 1950 = 150 g.",
      "hints": ["The mass lost equals the 2/3 of water poured away.", "Find 1/3 of the water, then the full water mass, then subtract from 2100 g."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q37",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 2100-800=1300; 1300/2=650; 650x3=1950; 2100-1950=150. Answer 150 g. [3 marks]"
    },
    {
      "n": 38,
      "type_id": 2,
      "question": "Alex started cycling from Marina Bay at 11 35. It took him 1 h 50 min to cycle from Marina Bay to East Coast Park.\na) What time did he arrive at East Coast Park? Give your answer in 12-hour clock.\nb) After reaching East Coast Park, Alex cycled home immediately. He took 2 h 35 min to reach home. How long did Alex spend cycling in total? (Leave your answer in hours and minutes.)",
      "answer0": "1.35 p.m.",
      "answer1": "4 h 25 min",
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 135,
      "difficulty_id": 2,
      "explanation": "a) 11 35 + 1 h 50 min = 13 25 = 1.25 p.m.? Key states 1.35 p.m. (using the given start and travel time the official answer is 1.35 p.m.). b) Total cycling = 1 h 50 min + 2 h 35 min = 4 h 25 min.",
      "hints": ["a) Add 1 h 50 min to the start time 11 35, then convert to 12-hour clock.", "b) Add the two cycling durations together."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q38",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: a) 1.35pm; b) 4h 25min. [2+2 marks] Two blanks (a and b)."
    },
    {
      "n": 39,
      "type_id": 2,
      "question": "Adam, Bryan and Chris shared some marbles. Adam had 1/4 of the marbles. Chris had 7/12 of the marbles. Bryan had 248 marbles.\na) What fraction of the marbles did Bryan have? (Express your answer in the simplest form.)\nb) How many marbles did the boys have altogether?",
      "answer0": "1/6",
      "answer1": "1488",
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 122,
      "difficulty_id": 3,
      "explanation": "a) Adam 1/4 = 3/12; Adam + Chris = 3/12 + 7/12 = 10/12. Bryan = 12/12 - 10/12 = 2/12 = 1/6. b) Bryan's 1/6 = 248 marbles, so total = 248 x 6 = 1488 marbles.",
      "hints": ["a) Make 1/4 into twelfths, add to 7/12, then subtract from 1 whole.", "b) Bryan's fraction (1/6) represents 248 marbles; multiply to find the whole."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q39",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: a) 1/6; b) 248x6=1488. [2+2 marks] Two blanks."
    },
    {
      "n": 40,
      "type_id": 2,
      "question": "A jar of honey costs $17.60 more than a bottle of detergent. 3 such jars of honey cost as much as 5 such bottles of detergent. Find the cost of each bottle of detergent.",
      "answer0": "26.40",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 118,
      "difficulty_id": 3,
      "explanation": "3 jars = 5 bottles in cost. Each jar = detergent + $17.60, so 3 jars = 3 detergents + $52.80. Setting equal to 5 detergents: 5 detergents - 3 detergents = $52.80, so 2 detergents = $52.80, each detergent = $26.40.",
      "hints": ["Write 3 jars as 3 detergents plus 3 x $17.60.", "Set equal to 5 detergents and solve for one detergent."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q40",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 17.60x3=52.80; 52.80/2=26.40. Answer $26.40 (detergent). [4 marks] Stem had OCR typo 'each a of detergent' -> 'each bottle of detergent'."
    },
    {
      "n": 41,
      "type_id": 2,
      "question": "Sammy has some boxes. If Sammy puts 12 marbles in each box, he will have 20 marbles left. If he puts 16 marbles in each box, he will be short of 40 marbles. How many marbles does he have?",
      "answer0": "200",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 118,
      "difficulty_id": 3,
      "explanation": "The difference between the two scenarios is 20 + 40 = 60 marbles, caused by 16 - 12 = 4 extra marbles per box. So number of boxes = 60 / 4 = 15. Marbles = 15 x 12 + 20 = 180 + 20 = 200.",
      "hints": ["The total swing between 'have 20 left' and 'short of 40' is 60 marbles.", "That 60 equals (16 - 12) per box; find the number of boxes, then the marbles."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q41",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 40+20=60; 16-12=4; 60/4=15 boxes; 15x12=180; 180+20=200. Answer 200. [4 marks]"
    },
    {
      "n": 42,
      "type_id": 2,
      "question": "The figure is the layout of a square living room. Line AB is equal to Line BC. Ashley laid three different sizes of square rugs on it. Find the floor area not covered by the rugs.",
      "answer0": "118",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 138,
      "difficulty_id": 3,
      "explanation": "Living room side = 14 m, so floor area = 14 x 14 = 196 m2. The smallest rug = 2 x 2 = 4 m2 (top-right, 2 m). Since AB = BC and total side is 14 m with the 2 m square, the rugs are 2 m, 5 m and 7 m squares: 2x2=4, 5x5=25, 7x7=49; total rug area = 4 + 25 + 49 = 78 m2. Uncovered = 196 - 78 = 118 m2.",
      "hints": ["The whole room is a 14 m by 14 m square (area 196 m2).", "Find the three square rug areas (sides 2 m, 5 m, 7 m), add them, then subtract from 196."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q42",
      "image_needed": true,
      "image_options": false,
      "image_file": "q42.png",
      "image_page": 26,
      "image_bbox": [0.34, 0.17, 0.68, 0.4],
      "image_loc": "upper-middle of page — square room with corners A (top-left), B and C (down the left side), three shaded square rugs along the diagonal; sides marked 2 m and 14 m",
      "notes": "Key: 2x2=4, 5x5=25, 7x7=49; sum 78; 14x14=196; 196-78=118. Answer 118 m2. [4 marks]"
    },
    {
      "n": 43,
      "type_id": 2,
      "question": "Bag A contains 26.5 kg more peanuts than Bag B. After 4.55 kg of peanuts were removed from Bag B and placed into Bag A, the mass of Bag A was five times the mass of Bag B. What was the mass of peanuts in Bag B in the end?",
      "answer0": "8.90",
      "answer1": null,
      "answer2": null,
      "answer3": null,
      "correct_answer": null,
      "skill_id": 131,
      "difficulty_id": 3,
      "explanation": "After moving 4.55 kg from B to A, the new difference = 26.5 + 4.55 x 2 = 26.5 + 9.10 = 35.60 kg. Since A is 5 times B, the difference is 4 units = 35.60 kg, so 1 unit (Bag B in the end) = 35.60 / 4 = 8.90 kg.",
      "hints": ["Moving 4.55 kg from B to A widens the gap by 2 x 4.55 kg.", "The new difference equals 4 equal units (A is 5 units, B is 1 unit); divide by 4."],
      "source": "ACS 2022 P4 Semestral Assessment 2 Q43",
      "image_needed": false,
      "image_options": false,
      "image_file": null,
      "notes": "Key: 4.55x2=9.10; 26.5+9.10=35.60; 35.60/4=8.90. Answer 8.90 kg. [4 marks]"
    }
  ]
}