The ratio of Ivan's age to Seth's age is 4 : 3. Last year, their average age was 20. How old will Seth be in 3 years' time?
| |
Ivan |
Seth |
Total |
| Before |
4 u - 1 |
3 u - 1 |
40 |
| Change |
+ 1 |
+ 1 |
|
| After |
4 u |
3 u |
42 |
Total age of Ivan and Seth this year
= 4 u + 3 u
= 7 u
Total age of Ivan and Seth this year
= 2 x 20 + 1 + 1
= 40 + 2
= 42
7 u = 42
1 u = 42 ÷ 7 = 6
Seth's age in 3 years' time
= 3 u + 3
= 3 x 6 + 3
= 18 + 3
= 21
Answer(s): 21
