Oscar is 4 times as old as his brother. In 20 years' time, Oscar will be 14 years less than twice of his brother's age. How old was Oscar 7 years ago?
|
Oscar |
Oscar's brother |
Difference |
Before |
4 u |
1 u |
3 u |
Change |
+ 20 |
+ 20 |
|
After |
2 p - 14 |
1 p |
1 p - 14 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 14 - 1 p
= 1 p - 14
The difference in their ages remains unchanged.
3 u = 1 p - 14
3 u + 14 =
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 + 14 = 1 u + 20
3 u - 1 u = 20 - 14
2 u = 6
1 u = 6 ÷ 2 = 3
Oscar's current age
= 4 u
= 4 x 3
= 12
Oscar's age 7 years ago
= 12 - 7
= 5
Answer(s): 5