Cathy's father is 4 times as old as her. Cathy will be 11 years old in 3 years' time. In how many years' time will Cathy's age be 60% that of her father's?
| |
Cathy's father |
Cathy |
Difference |
Before
(now) |
4x2 =
8 u |
1x2 =
2 u |
3x2 =
6 u |
| Change 1 |
+ 3 |
+ 3 |
|
| After 1 |
|
11 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x3 =
15 u |
3x3 =
9 u |
2x3 =
6 u |
60% =
60100 =
35 Cathy's father : Cathy = 5 : 3
The difference in age between Cathy's father and Cathy always remains the same. Make the difference in age between Cathy's father and Cathy the same. LCM of 3 and 2 is 6.
2 u + 3 = 11
2 u = 11 - 3
2 u = 8
1 u = 8 ÷ 2 = 4
Number of years' time when Cathy's age will be 60% that of her father's
= 15 u - 35
= 15 x 4 - 35
= 60 - 35
= 25
Answer(s): 25
