Sam's age is
13 of his grandmother's. His grandmother will be 65 years old in 20 years' time. In how many years' time will Sam's age be
35 that of his grandmother's?
| |
Sam |
His grandmother |
Difference |
| Before |
1x1 =
1 u |
3x1 =
3 u |
2x1 =
2 u |
| Change 1 |
+ 20 |
+ 20 |
|
| After |
|
65 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
3x1 =
3 u |
5x1 =
5 u |
2x1 =
2 u |
The age difference between Sam and his grandmother remains unchanged.
LCM of 2 and 2 is 2.
3 u + 20 = 65
3 u = 65 - 20
3 u = 45
1 u = 45 ÷ 3 = 15
Number of years' time when Sam's age will be
35 that of his grandmother's age
= 3 u - 1 u
= 2 u
= 2 x 15
= 30
Answer(s): 30
