Andy's mother is 3 times as old as him. His mother will be 37 years old in 10 years' time. In how many years' time will Andy's age be 80% that of his mother's?
| |
Andy's mother |
Andy |
Difference |
Before
(now) |
3x1 =
3 u |
1x1 =
1 u |
2x1 =
2 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After 1 |
37 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x2 =
10 u |
4x2 =
8 u |
1x2 =
2 u |
80% =
80100 =
45 Andy's mother : Andy = 5 : 4
The difference in age between Andy's mother and Andy always remains the same. Make the difference in age between Andy's mother and Andy the same. LCM of 2 and 1 is 2.
3 u + 10 = 37
3 u = 37 - 10
3 u = 27
1 u = 27 ÷ 3 = 9
Number of years' time when Andy's age will be 80% that of his mother's
= 10 u - 37
= 10 x 9 - 37
= 90 - 37
= 53
Answer(s): 53
