The ratio of John's age to Ken's age is 7 : 1. Next year, their average age will be 13. How old will John be in 3 years' time?
|
John |
Ken |
Total |
Before |
7 u |
1 u |
24 |
Change |
+ 1 |
+ 1 |
|
After |
7 u + 1 |
1 u + 1 |
26 |
Total age of John and Ken this year
= 7 u + 1 u
= 8 u
Total age of John and Ken this year
= 2 x 13 - 1 - 1
= 26 - 2
= 24
8 u = 24
1 u = 24 ÷ 8 = 3
John's age in 3 years' time
= 7 u + 3
= 7 x 3 + 3
= 21 + 3
= 24
Answer(s): 24