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.

Height of boy = 140 cm

Height of sister = 70 cm

Height of father = 170 cm

Step-by-step explanation:

Given that:

Combined height = 3.8 meters = 3.8*100 = 380 cm

Let,

b be the height of boy

s be the height of sister

f be the height of father

According to given statement;

b + s + f = 380     Eqn 1

b = 2s                  Eqn 2

b = f - 30             Eqn 3

Putting b=2s in Eqn 3

2s = f - 30

Putting these values in Eqn 1

Dividing both sides by 5

Putting f=170 in Eqn 3

b = 170 - 30

b = 140

Putting f=170 in Eqn 2

140 = 2s

s = 70

Hence,

Height of boy = 140 cm

Height of sister = 70 cm

Height of father = 170 cm