Rael's age is
37 of his grandmother's. His grandmother will be 71 years old in 15 years' time. In how many years' time will Rael's age be
23 that of his grandmother's?
|
Rael |
His grandmother |
Difference |
Before |
3x1 = 3 u |
7x1 = 7 u |
4x1 = 4 u |
Change 1 |
+ 15 |
+ 15 |
|
After |
|
71 |
|
Change 2 |
+ ? |
+ ? |
|
After 2 |
2x4 = 8 u |
3x4 = 12 u |
1x4 = 4 u |
The age difference between Rael and his grandmother remains unchanged.
LCM of 4 and 1 is 4.
7 u + 15 = 71
7 u = 71 - 15
7 u = 56
1 u = 56 ÷ 7 = 8
Number of years' time when Rael's age will be
23 that of his grandmother's age
= 8 u - 3 u
= 5 u
= 5 x 8
= 40
Answer(s): 40