Question

An 8-year-old boy is half his sister's age. When the boy is 12, how old will his sister be?

Answer 1

20 years

Explanation:

when the boy is 8 and half his sisters age his sister is 16

four years later the boy will be twelve, so if his sister was 16 four years later she will be 20

Answer 2

20 years old

Explanation:

Let n represent the age of the boy's sister then...

`8=(1)/(2)n`

Multiply both sides by 2

`n=16`

When the boy is 12, it will be 4 years from when he is 8 therefore...

16 + 4 = 20 years old