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