A and B can complete a piece of work in 27 days and 54 days, respectively. They completed the work in 9 days with the help of C. How many days will C take to complete eight-ninths (8/9) of the work 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?