SOLUTION STEPS (Set 7):
  1. Write all numbers with 3 decimal places: 0.600, 0.156, 0.510, 0.165.
  2. Compare tenths: 1 (in 0.156 and 0.165) is smallest. Compare hundredths: 5 < 6, so 0.156 is smaller.
  3. So 0.156 is the smallest. Match the second option.