Oscar is 4 times as old as his brother. In 19 years' time, Oscar will be 11 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 |
+ 19 |
+ 19 |
|
After |
2 p - 11 |
1 p |
1 p - 11 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 11 - 1 p
= 1 p - 11
The difference in their ages remains unchanged.
3 u = 1 p - 11
3 u + 11 =
1 p --- (1)
Age of Oscar's brother in 19 years' time
= 1 u + 19
1 u + 19 =
1 p --- (2)
(1) = (2)
3 u + 11 = 1 u + 19
3 u - 1 u = 19 - 11
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