Robbie and his father together are 313 cm. Take out Robbie’s 139 cm to find the father; the gap is the difference.

Robbie139 cmFather139 cm?difference313 cm

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

  1. Father → 313 − 139 = 174 cm
  2. Difference → 174 − 139 = 35 cm

The difference in height is 35 cm.

Check: 139 + 174 = 313 cm, and 174 − 139 = 35 cm. ✓