The ratio of John's age to Ben's age is 3 : 1. Next year, their average age will be 17. How old will John be in 8 years' time?
| |
John |
Ben |
Total |
| Before |
3 u |
1 u |
32 |
| Change |
+ 1 |
+ 1 |
|
| After |
3 u + 1 |
1 u + 1 |
34 |
Total age of John and Ben this year
= 3 u + 1 u
= 4 u
Total age of John and Ben this year
= 2 x 17 - 1 - 1
= 34 - 2
= 32
4 u = 32
1 u = 32 ÷ 4 = 8
John's age in 8 years' time
= 3 u + 8
= 3 x 8 + 8
= 24 + 8
= 32
Answer(s): 32
