30 boys are engaged to do a piece of work in 15 days but it is found that in 5 days, 3/5 work is completed. How many boys may be allowed to go off, so that the work may be finished on time?

If $\left(\frac{2}{9}\right)^{th}$ part of a tub is filled in 2 minutes, then the remaining part of the tub will be filled in :

A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

A and B can complete a piece of work in 30 days. B and C in 10 days, which C and A in 5 days. If all of them work together, the time taken in completing the work

P and Q can complete a job in 24 days working together. P can alone complete it in 32 days. Both of them worked together for 8 days and then P left. The number of days Q will take to complete the remaining job is:

P can complete a work in 20 days while Q is 25% more effiecent than P. Q worked for 6 days and left, remaining work is completed by R in 15 days. Find in how many days R can complete the whole work alone?

P and Q together can do a piece of work in 60 days. Q and R together can do it in 120 days. P and R together can do it in 90 days. In what time can Q alone do the same work?