Tina's father is 4 times as old as her. Tina will be 21 years old in 9 years' time. In how many years' time will Tina's age be 60% that of her father's?
| |
Tina's father |
Tina |
Difference |
Before
(now) |
4x2 =
8 u |
1x2 =
2 u |
3x2 =
6 u |
| Change 1 |
+ 9 |
+ 9 |
|
| After 1 |
|
21 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x3 =
15 u |
3x3 =
9 u |
2x3 =
6 u |
60% =
60100 =
35 Tina's father : Tina = 5 : 3
The difference in age between Tina's father and Tina always remains the same. Make the difference in age between Tina's father and Tina the same. LCM of 3 and 2 is 6.
2 u + 9 = 21
2 u = 21 - 9
2 u = 12
1 u = 12 ÷ 2 = 6
Number of years' time when Tina's age will be 60% that of her father's
= 15 u - 57
= 15 x 6 - 57
= 90 - 57
= 33
Answer(s): 33
