Usha's uncle is 5 times as old as her. Usha will be 15 years old in 9 years' time. In how many years' time will Usha's age be 70% that of her uncle's?
| |
Usha's uncle |
Usha |
Difference |
Before
(now) |
5x3 =
15 u |
1x3 =
3 u |
4x3 =
12 u |
| Change 1 |
+ 9 |
+ 9 |
|
| After 1 |
|
15 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x4 =
40 u |
7x4 =
28 u |
3x4 =
12 u |
70% =
70100 =
710 Usha's uncle : Usha = 10 : 7
The difference in age between Usha's uncle and Usha always remains the same. Make the difference in age between Usha's uncle and Usha the same. LCM of 4 and 3 is 12.
3 u + 9 = 15
3 u = 15 - 9
3 u = 6
1 u = 6 ÷ 3 = 2
Number of years' time when Usha's age will be 70% that of her uncle's
= 40 u - 39
= 40 x 2 - 39
= 80 - 39
= 41
Answer(s): 41
