Eric's age is
13 of his grandmother's. His grandmother will be 49 years old in 10 years' time. In how many years' time will Eric's age be
23 that of his grandmother's?
| |
Eric |
His grandmother |
Difference |
| Before |
1x1 =
1 u |
3x1 =
3 u |
2x1 =
2 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After |
|
49 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
2x2 =
4 u |
3x2 =
6 u |
1x2 =
2 u |
The age difference between Eric and his grandmother remains unchanged.
LCM of 2 and 1 is 2.
3 u + 10 = 49
3 u = 49 - 10
3 u = 39
1 u = 39 ÷ 3 = 13
Number of years' time when Eric's age will be
23 that of his grandmother's age
= 4 u - 1 u
= 3 u
= 3 x 13
= 39
Answer(s): 39
