Riya can complete a work in 21-day and Maya’s efficiency is half of the Riya. Find how many days Riya and Maya will take together to complete the whole work?

Two pipes, P and Q, together can fill a tank in 5 hours. If pipe P alone can fill the tank in 10 hours, then how much time (in hours) will pipe Q alone take to fill the tank?

25 persons, each working 10 hours a day, can complete 2 units of work in 4 days. How many days will it take for 10 persons working 9 hours a day to complete 18 units of work?

8 men and 3 women can do a piece of work in 7 days, whereas 5 men and 1 woman can do it in 12 days. How many men should assist 8 women so that the same work is completed in $$4\frac{1}{5}$$​ days?

A work can be completed by x persons in 50 days. Due to absence of 5 persons, the work was completed in 55 days. The value of x is

Pipes A and B can fill a tank in 12 hours and 18 hours, respectively. Pipe C is an emptying pipe. When all the three pipes are opened together for 8 hours, then 26/45 part of the tank is filled up. What part of the tank will be filled up by A and C together in 9 hours?

P can do work in 12 hr, Q in 6 hr. Together they must do double the work. Time required?

Pipe A can fill a tank in 13 hours, pipe B can fill the same tank in 26 hours and pipe C can fill the same tank in 17 hours. The time taken by them to fill the same tank if they operate together is: