# 12 men and 18 boys working 7 1/2 hours a day can do a certain work in 60 :

12 men and 18 boys working 7 1/2 hours a day can do a certain work in 60 If one man works equal to 2 boys, then the number of boys required to help 21 men to do twice the work in 50 days, working 9 hours a day, will be

- 30
- 42
- 48
- 90