A alone can do a piece of work in 10 days and B alone can do it in 15 days. In how many days will A and B together do the same work?

A pipe can fill a cistern in 9 hours. Due to a leak in its bottom, the cistern fills up in 10 hours. If the cistern is full, in how much time will it be emptied by the leak?

Pipe A can fill a cistern in 6 hours and pipe B can fill it in 8 hours. Both the pipes are opened and after two hours, pipe A is closed. How much time will B take to fill the remaining part of the tank?

A man can do a piece of work in 5 days. He and his son working together can finish it in 3 days. In how many days can the son do it alone?

A can do a job in 16 days and B can do the same job in 12 days. With the help of C. they can finish the job in 6 days only. Then, C alone can finish it in