George is 4 years old. His father is 21 years older than him. In how many years will George's father be 4 times as old as George?
| |
His father |
George |
Difference |
| Before |
25 |
4 |
21 |
| Change |
+ ? |
+ ? |
|
| After |
4 u |
1 u |
3 u |
The difference in the age between George and his father at first and in the end remains the same.
Difference in the age between George and his father
= 4 u - 1 u
= 3 u
3 u = 21
1 u = 21 ÷ 3 = 7
The increase in age of George and his father remains the same.
Number of years' time so George's father will be 4 times as old as George
= 7 - 4
= 3
Answer(s): 3
