If a brother and a sisters age is 4:3 and if the brother is 12 years old how old will the sister be?

Answer 1

b = brothers age

s = sisters age

A brother and a sisters age is 4:3 means:

b / s = 4 / 3

Brother is 12 years old so:

b / s = 4 / 3

12 / s = 4 / 3

Cross multiply

12 ∙ 3 = s ∙ 4

36 = 4 s

Divide both sides by 4

9 = s

s = 9 yrs old