Question

Vera and Vikki are sisters. Vera is 4 years old and Vikki is 13 years old. What age will each sister be when Vikki is twice as old as Vera?​

Answer 1

Answer:

Vikki=13+4×2=21 years

Vera = 21-9=12 years

Answer 2

Vera = 4 years

Vikki = 13 years

let the years to be past by be x

Vera's age when Vikki will be twice her age = 4 + x

Vikki's age when she will be twice Vera's age = 13 + x

Let Vikki's age after doubling be 2y

Let Vera's age after doubling be y

$\frac{4+x}{13+x} = \frac{y}{2y}$

$\frac{4+x}{13+x} = \frac{1}{2}$

Cross Multiplication

2 ( 4 + x ) = 13 + x

8 + 2x = 13 + x

2x - x = 13 - 8

x = 5

Therefore, after 5 years, Vikki will be twice the age of Vera.

Checking :-

Vikki ÷ Vera  = 2

( 13 + 5 ) ÷ ( 4 + 5 ) = 2

18 ÷ 9 = 2