Oscar is 5 times as old as his brother. In 17 years' time, Oscar will be 5 years less than twice of his brother's age. How old was Oscar 6 years ago?
|
Oscar |
Oscar's brother |
Difference |
Before |
5 u |
1 u |
4 u |
Change |
+ 17 |
+ 17 |
|
After |
2 p - 5 |
1 p |
1 p - 5 |
Difference in their ages at first
= 5 u - 1 u
= 4 u
Difference in their ages in the end
= 2 p - 5 - 1 p
= 1 p - 5
The difference in their ages remains unchanged.
4 u = 1 p - 5
4 u + 5 =
1 p --- (1)
Age of Oscar's brother in 17 years' time
= 1 u + 17
1 u + 17 =
1 p --- (2)
(1) = (2)
4 u + 5 = 1 u + 17
4 u - 1 u = 17 - 5
3 u = 12
1 u = 12 ÷ 3 = 4
Oscar's current age
= 5 u
= 5 x 4
= 20
Oscar's age 6 years ago
= 20 - 6
= 14
Answer(s): 14