15 men ,working 8 hours a day, can build a wall in 20 days , in how many days will 20 men build the same wall working 5 hours a day?

10 men working 8 hours day can do a work in 30 days. In how many days will 12 men working 4 hours a day take do the same work?

If 20 men working 7 hours a day can do a piece of work in 10 days, in how many days will 15 men working 8 hours a day do the same piece of work?

If 3 men and 4 women can build a wall in 43 days , in how many days can 7 men and 5 women build this wall ?

30 men working 5 hours a day can do a task in 16 days in how many days will 40 men working 6 hours a day fo the same task ? A. 12 days B. 10 days C. 15 days D. 18 days