Justin is 3 years old. His uncle is 21 years older than him. In how many years will Justin's uncle be 4 times as old as Justin?
| |
His uncle |
Justin |
Difference |
| Before |
24 |
3 |
21 |
| Change |
+ ? |
+ ? |
|
| After |
4 u |
1 u |
3 u |
The difference in the age between Justin and his uncle at first and in the end remains the same.
Difference in the age between Justin and his uncle
= 4 u - 1 u
= 3 u
3 u = 21
1 u = 21 ÷ 3 = 7
The increase in age of Justin and his uncle remains the same.
Number of years' time so Justin's uncle will be 4 times as old as Justin
= 7 - 3
= 4
Answer(s): 4
