Oscar is 4 times as old as his brother. In 20 years' time, Oscar will be 6 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 |
+ 20 |
+ 20 |
|
After |
2 p - 6 |
1 p |
1 p - 6 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 6 - 1 p
= 1 p - 6
The difference in their ages remains unchanged.
3 u = 1 p - 6
3 u + 6 =
1 p --- (1)
Age of Oscar's brother in 20 years' time
= 1 u + 20
1 u + 20 =
1 p --- (2)
(1) = (2)
3 u + 6 = 1 u + 20
3 u - 1 u = 20 - 6
2 u = 14
1 u = 14 ÷ 2 = 7
Oscar's current age
= 4 u
= 4 x 7
= 28
Oscar's age 8 years ago
= 28 - 8
= 20
Answer(s): 20