Noor, twelve years old, is three times as old as her sister. How many old will Noor be when she is twice as old as her sister?
Noor, twelve years old, is three times as old as her sister. How many old will Noor be when she is twice as old as her sister?
Explanation
Let's denote Noor's current age as N and her sister's current age as S.
Given:
N = 12 years
N = 3S
12 = 3S
S = 4 years
Let's denote the number of years that will pass before Noor is twice as old as her sister as x.
Noor's age = 12 + x
Sister's age = 4 + x
Given:
12 + x = 2(4 + x)
12 + x = 8 + 2x
12 - 8 = 2x - x
4 = x
Noor's age = 12 + 4 = 16