Mark's age is
13 of his granduncle's. His granduncle will be 62 years old in 20 years' time. In how many years' time will Mark's age be
12 that of his granduncle's?
| |
Mark |
His granduncle |
Difference |
| Before |
1x1 =
1 u |
3x1 =
3 u |
2x1 =
2 u |
| Change 1 |
+ 20 |
+ 20 |
|
| After |
|
62 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x2 =
2 u |
2x2 =
4 u |
1x2 =
2 u |
The age difference between Mark and his granduncle remains unchanged.
LCM of 2 and 1 is 2.
3 u + 20 = 62
3 u = 62 - 20
3 u = 42
1 u = 42 ÷ 3 = 14
Number of years' time when Mark's age will be
12 that of his granduncle's age
= 2 u - 1 u
= 1 u
= 1 x 14
= 14
Answer(s): 14
