Question

The sum of the ages of Kristen and Ben is 32. Four years ago Kristen was twice as old as Ben. How old are they both now?

Answer 1

Let us say that:

K = age of Kristen

B = age of Ben

 

From the problem, we make the equations:

eqtn 1: K + B = 32

eqtn 2: (K – 4) = 2 (B – 4)

 

Simplifying eqtn 2:

K – 4 = 2 B – 8

K = 2 B – 4

 

Plugging in this to eqtn 2:

(2 B – 4) + B = 32

3 B – 4 = 32

3 B = 36

B = 12

 

From eqtn 2:

K = 2 B – 4 = 2 (12) – 4 = 20

 

So Kristen is 20 while Ben is 12.