Jack's current age is 3 times as old as Justin's age years ago. Today, Justin's age is Jack's age the same number of years ago. How old is Jack's age now if the total of their current age is 35?
| |
Jack |
Justin |
Difference |
Total |
| Before |
1 p |
1 u |
1 p - 1 u |
|
| Change |
+ ? |
+ ? |
|
|
| After |
3 u |
1 p |
3 u - 1 p |
35 |
Total age of Jack and Justin today = 3 u + 1 p
3 u + 1 p = 35 --- (1)
The difference in Jack's age and Justin'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 = 35
3 u + 2 u = 35
5 u = 35
1 u = 35 ÷ 5 = 7
Jack's age now
= 3 u
= 3 x 7
= 21
Answer(s): 21
