Fred's age is
16 of his grandfather's. His grandfather will be 63 years old in 15 years' time. In how many years' time will Fred's age be
12 that of his grandfather's?
| |
Fred |
His grandfather |
Difference |
| Before |
1x1 =
1 u |
6x1 =
6 u |
5x1 =
5 u |
| Change 1 |
+ 15 |
+ 15 |
|
| After |
|
63 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x5 =
5 u |
2x5 =
10 u |
1x5 =
5 u |
The age difference between Fred and his grandfather remains unchanged.
LCM of 5 and 1 is 5.
6 u + 15 = 63
6 u = 63 - 15
6 u = 48
1 u = 48 ÷ 6 = 8
Number of years' time when Fred's age will be
12 that of his grandfather's age
= 5 u - 1 u
= 4 u
= 4 x 8
= 32
Answer(s): 32
