Michael's age is
25 of his grandmother's. His grandmother will be 85 years old in 10 years' time. In how many years' time will Michael's age be
12 that of his grandmother's?
| |
Michael |
His grandmother |
Difference |
| Before |
2x1 =
2 u |
5x1 =
5 u |
3x1 =
3 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After |
|
85 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x3 =
3 u |
2x3 =
6 u |
1x3 =
3 u |
The age difference between Michael and his grandmother remains unchanged.
LCM of 3 and 1 is 3.
5 u + 10 = 85
5 u = 85 - 10
5 u = 75
1 u = 75 ÷ 5 = 15
Number of years' time when Michael's age will be
12 that of his grandmother's age
= 3 u - 2 u
= 1 u
= 1 x 15
= 15
Answer(s): 15
