Riordan's age is
15 of his grandmother's. His grandmother will be 49 years old in 9 years' time. In how many years' time will Riordan's age be
23 that of his grandmother's?
| |
Riordan |
His grandmother |
Difference |
| Before |
1x1 =
1 u |
5x1 =
5 u |
4x1 =
4 u |
| Change 1 |
+ 9 |
+ 9 |
|
| After |
|
49 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
2x4 =
8 u |
3x4 =
12 u |
1x4 =
4 u |
The age difference between Riordan and his grandmother remains unchanged.
LCM of 4 and 1 is 4.
5 u + 9 = 49
5 u = 49 - 9
5 u = 40
1 u = 40 ÷ 5 = 8
Number of years' time when Riordan's age will be
23 that of his grandmother's age
= 8 u - 1 u
= 7 u
= 7 x 8
= 56
Answer(s): 56
