Question

Kim's age is twice that of her sister. When you add Kim's age to her sister's age, you get 42. How old is each sister?

(a) Write an equation that represents the situation. Explain any variable used.
(b) Solve the equation from Part (a). Show your work. State your solution as a complete sentence.

Answer 1

a: K = 2s

K + s = 42

b: 2s + s = 42

K = 28

s = 14

Explanation:

1. Come up with equations based on the information given.

K = Kim

s = sister

Kim is twice of her sister -> K = 2s

When you add Kim's age to her sister's age, you get 42 -> K + s = 42

2. Substitue for K to find out the value of s

K = 2s

2s + s = 42

3. Solve for s

s = 42/3

s= 14

4. Solve for K

K = 2s

K = 2*14

K = 28