Fanny's mother is 4 times as old as her. Fanny will be 20 years old in 10 years' time. In how many years' time will Fanny's age be 60% that of her mother's?
| |
Fanny's mother |
Fanny |
Difference |
Before
(now) |
4x2 =
8 u |
1x2 =
2 u |
3x2 =
6 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After 1 |
|
20 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x3 =
15 u |
3x3 =
9 u |
2x3 =
6 u |
60% =
60100 =
35 Fanny's mother : Fanny = 5 : 3
The difference in age between Fanny's mother and Fanny always remains the same. Make the difference in age between Fanny's mother and Fanny the same. LCM of 3 and 2 is 6.
2 u + 10 = 20
2 u = 20 - 10
2 u = 10
1 u = 10 ÷ 2 = 5
Number of years' time when Fanny's age will be 60% that of her mother's
= 15 u - 50
= 15 x 5 - 50
= 75 - 50
= 25
Answer(s): 25
