Boys = 1 unit, girls = 4 units. The 24 more girls is the gap of 3 units. Total children = 5 units.

Boys1Girls111124 more = 3 units

Plain numbers are given; italic underlined numbers are worked out.

  1. Girls − Boys = 3 units → 24
  2. 1 unit → 24 ÷ 3 = 8 (boys)
  3. Children = 5 units → 5 × 8 = 40

There are 40 children.

Check: boys 8 + girls 32 = 40, and 32 − 8 = 24. ✓