Bobby is 4 years old. His uncle is 18 years older than him. In how many years will Bobby's uncle be 3 times as old as Bobby?
| |
His uncle |
Bobby |
Difference |
| Before |
22 |
4 |
18 |
| Change |
+ ? |
+ ? |
|
| After |
3 u |
1 u |
2 u |
The difference in the age between Bobby and his uncle at first and in the end remains the same.
Difference in the age between Bobby and his uncle
= 3 u - 1 u
= 2 u
2 u = 18
1 u = 18 ÷ 2 = 9
The increase in age of Bobby and his uncle remains the same.
Number of years' time so Bobby's uncle will be 3 times as old as Bobby
= 9 - 4
= 5
Answer(s): 5
