Question

A boy is twice as tall as his little sister and 30cm shorter than his father. Their combined height is 3.8 meters. Find (in cm) the height of each person.

Answer 1

Call the sister's height x. The boy is twice as tall, so that's 2x. The father is 30 cm taller than the boy, so his height is 2x + 30. The combined height is 3.8m, which is 380cm. Now you can write an equation

x + 2x + 2x + 30 = 380

collect like terms

5x = 350

x = 70

the sister is 70cm tall, the boy is 2*70 = 140 cm, and the father is 140 + 30 = 170cm

Check that the heights add up to 3.8m: 70 + 140 + 170 = 380 cm = 3.8m. Correct

Explanation:

hope it helps