Oscar is 4 times as old as his brother. In 18 years' time, Oscar will be 2 years less than twice of his brother's age. How old was Oscar 2 years ago?
|
Oscar |
Oscar's brother |
Difference |
Before |
4 u |
1 u |
3 u |
Change |
+ 18 |
+ 18 |
|
After |
2 p - 2 |
1 p |
1 p - 2 |
Difference in their ages at first
= 4 u - 1 u
= 3 u
Difference in their ages in the end
= 2 p - 2 - 1 p
= 1 p - 2
The difference in their ages remains unchanged.
3 u = 1 p - 2
3 u + 2 =
1 p --- (1)
Age of Oscar's brother in 18 years' time
= 1 u + 18
1 u + 18 =
1 p --- (2)
(1) = (2)
3 u + 2 = 1 u + 18
3 u - 1 u = 18 - 2
2 u = 16
1 u = 16 ÷ 2 = 8
Oscar's current age
= 4 u
= 4 x 8
= 32
Oscar's age 2 years ago
= 32 - 2
= 30
Answer(s): 30