36.
3 pumps , working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day ?

37.
If 5 men or 7 women can earn Rs. 5250 per day, how much would 7 men and 13 women earn per day ?

38.
3 men or 6 women can do a piece of work in 20 days. In how days will 12 men and 8 women do the same work ?

39.
49 pumps can empty a reservoir in $$6\frac{1}{2}$$ days, working 8 hours a day. If 196 pumps are used for 5 hours each day, then the same work will be complete in ?

40.
30 labourers working 7 hours a day can finish a piece of work in 18 days. If the labourers work 6 hours a day, then the number of labourers to finish the same piece of work in 30 days, will be ?