Use the top-level ratio 2:3 to find how many pens and pencils there are, then break each group down using sub-ratios.
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• Top-level ratio 2:3 means 5 units in total.
• 100 ÷ 5 = 20 per unit.
• Pens: 2 × 20 = 40
• Pencils: 3 × 20 = 60
For the pens (sub-ratio 3 + 2):
• 5 parts = 8 per part
• black: 3 × 8 = 24
• blue: 2 × 8 = 16
For the pencils (sub-ratio 1 + 4):
• 5 parts = 12 per part
• black: 1 × 12 = 12
• blue: 4 × 12 = 48
Total blue: 16 + 48 = 64.
Check: 40 + 60 = 100 = total (100). ✓
Final Answer: 64