David's uncle is 6 times as old as him. His uncle will be 29 years old in 5 years' time. In how many years' time will David's age be 60% that of his uncle's?
| |
David's uncle |
David |
Difference |
Before
(now) |
6x2 =
12 u |
1x2 =
2 u |
5x2 =
10 u |
| Change 1 |
+ 5 |
+ 5 |
|
| After 1 |
29 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x5 =
25 u |
3x5 =
15 u |
2x5 =
10 u |
60% =
60100 =
35 David's uncle : David = 5 : 3
The difference in age between David's uncle and David always remains the same. Make the difference in age between David's uncle and David the same. LCM of 5 and 2 is 10.
12 u + 5 = 29
12 u = 29 - 5
12 u = 24
1 u = 24 ÷ 12 = 2
Number of years' time when David's age will be 60% that of his uncle's
= 25 u - 29
= 25 x 2 - 29
= 50 - 29
= 21
Answer(s): 21
