Pierre's age is
25 of his grandmother's. His grandmother will be 66 years old in 6 years' time. In how many years' time will Pierre's age be
12 that of his grandmother's?
| |
Pierre |
His grandmother |
Difference |
| Before |
2x1 =
2 u |
5x1 =
5 u |
3x1 =
3 u |
| Change 1 |
+ 6 |
+ 6 |
|
| After |
|
66 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x3 =
3 u |
2x3 =
6 u |
1x3 =
3 u |
The age difference between Pierre and his grandmother remains unchanged.
LCM of 3 and 1 is 3.
5 u + 6 = 66
5 u = 66 - 6
5 u = 60
1 u = 60 ÷ 5 = 12
Number of years' time when Pierre's age will be
12 that of his grandmother's age
= 3 u - 2 u
= 1 u
= 1 x 12
= 12
Answer(s): 12
