Archie's age is
25 of his grandfather's. His grandfather will be 58 years old in 18 years' time. In how many years' time will Archie's age be
23 that of his grandfather's?
| |
Archie |
His grandfather |
Difference |
| Before |
2x1 =
2 u |
5x1 =
5 u |
3x1 =
3 u |
| Change 1 |
+ 18 |
+ 18 |
|
| After |
|
58 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
2x3 =
6 u |
3x3 =
9 u |
1x3 =
3 u |
The age difference between Archie and his grandfather remains unchanged.
LCM of 3 and 1 is 3.
5 u + 18 = 58
5 u = 58 - 18
5 u = 40
1 u = 40 ÷ 5 = 8
Number of years' time when Archie's age will be
23 that of his grandfather's age
= 6 u - 2 u
= 4 u
= 4 x 8
= 32
Answer(s): 32
