Abi's father is 4 times as old as her. Abi will be 13 years old in 7 years' time. In how many years' time will Abi's age be 60% that of her father's?
| |
Abi's father |
Abi |
Difference |
Before
(now) |
4x2 =
8 u |
1x2 =
2 u |
3x2 =
6 u |
| Change 1 |
+ 7 |
+ 7 |
|
| After 1 |
|
13 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x3 =
15 u |
3x3 =
9 u |
2x3 =
6 u |
60% =
60100 =
35 Abi's father : Abi = 5 : 3
The difference in age between Abi's father and Abi always remains the same. Make the difference in age between Abi's father and Abi the same. LCM of 3 and 2 is 6.
2 u + 7 = 13
2 u = 13 - 7
2 u = 6
1 u = 6 ÷ 2 = 3
Number of years' time when Abi's age will be 60% that of her father's
= 15 u - 31
= 15 x 3 - 31
= 45 - 31
= 14
Answer(s): 14
