Bobby's mother is 5 times as old as him. His mother will be 43 years old in 3 years' time. In how many years' time will Bobby's age be 60% that of his mother's?
| |
Bobby's mother |
Bobby |
Difference |
Before
(now) |
5x1 =
5 u |
1x1 =
1 u |
4x1 =
4 u |
| Change 1 |
+ 3 |
+ 3 |
|
| After 1 |
43 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x2 =
10 u |
3x2 =
6 u |
2x2 =
4 u |
60% =
60100 =
35 Bobby's mother : Bobby = 5 : 3
The difference in age between Bobby's mother and Bobby always remains the same. Make the difference in age between Bobby's mother and Bobby the same. LCM of 4 and 2 is 4.
5 u + 3 = 43
5 u = 43 - 3
5 u = 40
1 u = 40 ÷ 5 = 8
Number of years' time when Bobby's age will be 60% that of his mother's
= 10 u - 43
= 10 x 8 - 43
= 80 - 43
= 37
Answer(s): 37
