Seth is 5 years old. His mother is 20 years older than him. In how many years will Seth's mother be 3 times as old as Seth?
| |
His mother |
Seth |
Difference |
| Before |
25 |
5 |
20 |
| Change |
+ ? |
+ ? |
|
| After |
3 u |
1 u |
2 u |
The difference in the age between Seth and his mother at first and in the end remains the same.
Difference in the age between Seth and his mother
= 3 u - 1 u
= 2 u
2 u = 20
1 u = 20 ÷ 2 = 10
The increase in age of Seth and his mother remains the same.
Number of years' time so Seth's mother will be 3 times as old as Seth
= 10 - 5
= 5
Answer(s): 5
