David's age is
25 of his grandaunt's. His grandaunt will be 57 years old in 7 years' time. In how many years' time will David's age be
710 that of his grandaunt's?
| |
David |
His grandaunt |
Difference |
| Before |
2x1 =
2 u |
5x1 =
5 u |
3x1 =
3 u |
| Change 1 |
+ 7 |
+ 7 |
|
| After |
|
57 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
7x1 =
7 u |
10x1 =
10 u |
3x1 =
3 u |
The age difference between David and his grandaunt remains unchanged.
LCM of 3 and 3 is 3.
5 u + 7 = 57
5 u = 57 - 7
5 u = 50
1 u = 50 ÷ 5 = 10
Number of years' time when David's age will be
710 that of his grandaunt's age
= 7 u - 2 u
= 5 u
= 5 x 10
= 50
Answer(s): 50
