Gem's uncle is 3 times as old as her. Gem will be 20 years old in 11 years' time. In how many years' time will Gem's age be 70% that of her uncle's?
| |
Gem's uncle |
Gem |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 11 |
+ 11 |
|
| After 1 |
|
20 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Gem's uncle : Gem = 10 : 7
The difference in age between Gem's uncle and Gem always remains the same. Make the difference in age between Gem's uncle and Gem the same. LCM of 2 and 3 is 6.
3 u + 11 = 20
3 u = 20 - 11
3 u = 9
1 u = 9 ÷ 3 = 3
Number of years' time when Gem's age will be 70% that of her uncle's
= 20 u - 38
= 20 x 3 - 38
= 60 - 38
= 22
Answer(s): 22
