The ratio of Justin's age to Lee's age is 3 : 1. Next year, their average age will be 15. How old will Justin be in 7 years' time?
| |
Justin |
Lee |
Total |
| Before |
3 u |
1 u |
28 |
| Change |
+ 1 |
+ 1 |
|
| After |
3 u + 1 |
1 u + 1 |
30 |
Total age of Justin and Lee this year
= 3 u + 1 u
= 4 u
Total age of Justin and Lee this year
= 2 x 15 - 1 - 1
= 30 - 2
= 28
4 u = 28
1 u = 28 ÷ 4 = 7
Justin's age in 7 years' time
= 3 u + 7
= 3 x 7 + 7
= 21 + 7
= 28
Answer(s): 28
