The ratio of Mark's age to Seth's age is 5 : 1. Next year, their average age will be 10. How old will Mark be in 4 years' time?
| |
Mark |
Seth |
Total |
| Before |
5 u |
1 u |
18 |
| Change |
+ 1 |
+ 1 |
|
| After |
5 u + 1 |
1 u + 1 |
20 |
Total age of Mark and Seth this year
= 5 u + 1 u
= 6 u
Total age of Mark and Seth this year
= 2 x 10 - 1 - 1
= 20 - 2
= 18
6 u = 18
1 u = 18 ÷ 6 = 3
Mark's age in 4 years' time
= 5 u + 4
= 5 x 3 + 4
= 15 + 4
= 19
Answer(s): 19
