The ratio of Tommy's age to Bobby's age is 3 : 1. Next year, their average age will be 15. How old will Tommy be in 9 years' time?
| |
Tommy |
Bobby |
Total |
| Before |
3 u |
1 u |
28 |
| Change |
+ 1 |
+ 1 |
|
| After |
3 u + 1 |
1 u + 1 |
30 |
Total age of Tommy and Bobby this year
= 3 u + 1 u
= 4 u
Total age of Tommy and Bobby this year
= 2 x 15 - 1 - 1
= 30 - 2
= 28
4 u = 28
1 u = 28 ÷ 4 = 7
Tommy's age in 9 years' time
= 3 u + 9
= 3 x 7 + 9
= 21 + 9
= 30
Answer(s): 30
