A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?

A can do a piece of work in 10 days and B can do it in 15 days. If they work together, in how many days will the work be completed?

If 10 persons can finish a task in 20 days, how many days will 20 persons take to finish the same task?

A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is:

A cistern can be filled by two pipes A and B in 12 and 15 hours respectively. If both are opened together, how long will it take to fill the cistern?

If 5 persons can weave 5 mats in 5 days, how many mats will 10 persons weave in 10 days?

If 15 workers can build a wall in 48 hours, how many workers will be required to do the same work in 30 hours?

If 6 men and 8 boys can do a piece of work in 10 days, while 26 men and 48 boys can do the same in 2 days, what is the time taken by 15 men and 20 boys?