Answer:
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
Step-by-step explanation:
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