Ravi takes 80% longer than Rohit to complete a wall. If together they complete the wall in 20 days, how long will Rohit take to complete it alone?

If P and Q together can complete a piece of work in 15 days and P alone can do it in 45 days, in how many days can Q alone complete that work?

A can lay a railway track between two stations in 16 days and B can do the same job in 12 days. With the help of C, they finished the job in 4 days. In how many days can C alone do the job?

P takes twice as much time as Q or thrice as much time as R to finish a piece of work. Working together, they can complete the work in 2 days. In how many days can Q alone complete the work?

A and B take 5 hours and 20 hours respectively to complete a piece of work. A works for 1 hour and then B works for 2 hours. How much work is remaining now?

A can do a piece of work in 15 days and B in 20 days. If they work together for 4 days, what fraction of the work is left?

A can complete a piece of work in 10 days and B can complete it in 25 days. If they work on alternate days, starting with B on the first day, in how many days will the work be finished?

A can complete a piece of work in 17 days. The portion of work remaining after A works alone for 7 days is:

A and B together can complete a work in 9 days. If A alone can do it in 36 days, then B alone can do three-fourth of the same work in ______________ days.