Rael's age is
25 of his grandmother's. His grandmother will be 87 years old in 17 years' time. In how many years' time will Rael's age be
12 that of his grandmother's?
| |
Rael |
His grandmother |
Difference |
| Before |
2x1 =
2 u |
5x1 =
5 u |
3x1 =
3 u |
| Change 1 |
+ 17 |
+ 17 |
|
| After |
|
87 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x3 =
3 u |
2x3 =
6 u |
1x3 =
3 u |
The age difference between Rael and his grandmother remains unchanged.
LCM of 3 and 1 is 3.
5 u + 17 = 87
5 u = 87 - 17
5 u = 70
1 u = 70 ÷ 5 = 14
Number of years' time when Rael's age will be
12 that of his grandmother's age
= 3 u - 2 u
= 1 u
= 1 x 14
= 14
Answer(s): 14
