Tommy's age is
37 of his grandmother's. His grandmother will be 83 years old in 6 years' time. In how many years' time will Tommy's age be
12 that of his grandmother's?
| |
Tommy |
His grandmother |
Difference |
| Before |
3x1 =
3 u |
7x1 =
7 u |
4x1 =
4 u |
| Change 1 |
+ 6 |
+ 6 |
|
| After |
|
83 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
1x4 =
4 u |
2x4 =
8 u |
1x4 =
4 u |
The age difference between Tommy and his grandmother remains unchanged.
LCM of 4 and 1 is 4.
7 u + 6 = 83
7 u = 83 - 6
7 u = 77
1 u = 77 ÷ 7 = 11
Number of years' time when Tommy's age will be
12 that of his grandmother's age
= 4 u - 3 u
= 1 u
= 1 x 11
= 11
Answer(s): 11
