Oscar is 4 times as old as his brother. In 17 years' time, Oscar will be 13 years less than twice of his brother's age. How old was Oscar 4 years ago?
| |
Oscar |
Oscar's brother |
Difference |
| Before |
4 u |
1 u |
3 u |
| Change |
+ 17 |
+ 17 |
|
| After |
2 p - 13 |
1 p |
1 p - 13 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 13 - 1 p
= 1 p - 13
The difference in their ages remains unchanged.
3 u = 1 p - 13
3 u + 13 =
1 p --- (1)
Age of Oscar's brother in 17 years' time
= 1 u + 17
1 u + 17 =
1 p --- (2)
(1) = (2)
3 u + 13 = 1 u + 17
3 u - 1 u = 17 - 13
2 u = 4
1 u = 4 ÷ 2 = 2
Oscar's current age
= 4 u
= 4 x 2
= 8
Oscar's age 4 years ago
= 8 - 4
= 4
Answer(s): 4
