A and B can do a piece of work in 11 days and 55 days, respectively. Both work together for 3 days and then A leaves. B completes the remaining work alone. In how many days was the whole work completed?

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?