The ratio of Simon's age to Jack's age is 5 : 2. Last year, their average age was 20. How old will Jack be in 3 years' time?
| |
Simon |
Jack |
Total |
| Before |
5 u - 1 |
2 u - 1 |
40 |
| Change |
+ 1 |
+ 1 |
|
| After |
5 u |
2 u |
42 |
Total age of Simon and Jack this year
= 5 u + 2 u
= 7 u
Total age of Simon and Jack this year
= 2 x 20 + 1 + 1
= 40 + 2
= 42
7 u = 42
1 u = 42 ÷ 7 = 6
Jack's age in 3 years' time
= 2 u + 3
= 2 x 6 + 3
= 12 + 3
= 15
Answer(s): 15
