When Mr John is 42 years old, his child is 3 years old. In how many years will he be 4 times as old as his child?
| |
Mr John |
His child |
Difference |
| Before |
42 |
3 |
39 |
| Change |
+ ? |
+ ? |
|
| After |
4 u |
1 u |
3 u |
The difference in the age between Mr John and his child at first and in the end remains the same.
Difference in the age between Mr John and his child
= 4 u - 1 u
= 3 u
3 u = 42 - 3
3 u = 39
1 u = 39 ÷ 3 = 13
Number of years' time so Mr John will be 4 times as old as his child
= 13 - 3
= 10
Answer(s): 10
