Oscar is 4 times as old as his brother. In 18 years' time, Oscar will be 10 years less than twice of his brother's age. How old was Oscar 8 years ago?
| |
Oscar |
Oscar's brother |
Difference |
| Before |
4 u |
1 u |
3 u |
| Change |
+ 18 |
+ 18 |
|
| After |
2 p - 10 |
1 p |
1 p - 10 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 10 - 1 p
= 1 p - 10
The difference in their ages remains unchanged.
3 u = 1 p - 10
3 u + 10 =
1 p --- (1)
Age of Oscar's brother in 18 years' time
= 1 u + 18
1 u + 18 =
1 p --- (2)
(1) = (2)
3 u + 10 = 1 u + 18
3 u - 1 u = 18 - 10
2 u = 8
1 u = 8 ÷ 2 = 4
Oscar's current age
= 4 u
= 4 x 4
= 16
Oscar's age 8 years ago
= 16 - 8
= 8
Answer(s): 8
