Carl's age is
13 of his grandfather's. His grandfather will be 49 years old in 4 years' time. In how many years' time will Carl's age be
12 that of his grandfather's?
| |
Carl |
His grandfather |
Difference |
| Before |
1x1 =
1 u |
3x1 =
3 u |
2x1 =
2 u |
| Change 1 |
+ 4 |
+ 4 |
|
| After |
|
49 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x2 =
2 u |
2x2 =
4 u |
1x2 =
2 u |
The age difference between Carl and his grandfather remains unchanged.
LCM of 2 and 1 is 2.
3 u + 4 = 49
3 u = 49 - 4
3 u = 45
1 u = 45 ÷ 3 = 15
Number of years' time when Carl's age will be
12 that of his grandfather's age
= 2 u - 1 u
= 1 u
= 1 x 15
= 15
Answer(s): 15
