Cody's current age is 3 times as old as Sean's age years ago. Today, Sean's age is Cody's age the same number of years ago. How old is Sean's age now if the total of their current age is 20?
| |
Cody |
Sean |
Difference |
Total |
| Before |
1 p |
1 u |
1 p - 1 u |
|
| Change |
+ ? |
+ ? |
|
|
| After |
3 u |
1 p |
3 u - 1 p |
20 |
Total age of Cody and Sean today = 3 u + 1 p
3 u + 1 p = 20 --- (1)
The difference in Cody's age and Sean's age remains the same.
3 u - 1 p = 1 p - 1 u
3 u + 1 u = 1 p + 1 p
4 u = 2 p
2 u = 1 p
Substitute 1 p = 2 u into (1).
3 u + 1 p = 20
3 u + 2 u = 20
5 u = 20
1 u = 20 ÷ 5 = 4
Cody's age now
= 20 - 3 u
= 20 - 3 x 4
= 20 - 12
= 8
Answer(s): 8
