Riordan's age is
37 of his grandaunt's. His grandaunt will be 79 years old in 2 years' time. In how many years' time will Riordan's age be
12 that of his grandaunt's?
|
Riordan |
His grandaunt |
Difference |
Before |
3x1 = 3 u |
7x1 = 7 u |
4x1 = 4 u |
Change 1 |
+ 2 |
+ 2 |
|
After |
|
79 |
|
Change 2 |
+ ? |
+ ? |
|
After 2 |
1x4 = 4 u |
2x4 = 8 u |
1x4 = 4 u |
The age difference between Riordan and his grandaunt remains unchanged.
LCM of 4 and 1 is 4.
7 u + 2 = 79
7 u = 79 - 2
7 u = 77
1 u = 77 ÷ 7 = 11
Number of years' time when Riordan's age will be
12 that of his grandaunt's age
= 4 u - 3 u
= 1 u
= 1 x 11
= 11
Answer(s): 11