Oscar's age is
15 of his grandaunt's. His grandaunt will be 79 years old in 19 years' time. In how many years' time will Oscar's age be
12 that of his grandaunt's?
| |
Oscar |
His grandaunt |
Difference |
| Before |
1x1 =
1 u |
5x1 =
5 u |
4x1 =
4 u |
| Change 1 |
+ 19 |
+ 19 |
|
| After |
|
79 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x4 =
4 u |
2x4 =
8 u |
1x4 =
4 u |
The age difference between Oscar and his grandaunt remains unchanged.
LCM of 4 and 1 is 4.
5 u + 19 = 79
5 u = 79 - 19
5 u = 60
1 u = 60 ÷ 5 = 12
Number of years' time when Oscar's age will be
12 that of his grandaunt's age
= 4 u - 1 u
= 3 u
= 3 x 12
= 36
Answer(s): 36
