The ratio of David's age to Ivan's age is 9 : 1. Next year, their average age will be 16. How old will David be in 5 years' time?
| |
David |
Ivan |
Total |
| Before |
9 u |
1 u |
30 |
| Change |
+ 1 |
+ 1 |
|
| After |
9 u + 1 |
1 u + 1 |
32 |
Total age of David and Ivan this year
= 9 u + 1 u
= 10 u
Total age of David and Ivan this year
= 2 x 16 - 1 - 1
= 32 - 2
= 30
10 u = 30
1 u = 30 ÷ 10 = 3
David's age in 5 years' time
= 9 u + 5
= 9 x 3 + 5
= 27 + 5
= 32
Answer(s): 32
