Ajay can do a piece of work in 20 days and Vijay can do the same work in 22 days. In how many days will they complete the work together if they work on alternate days and the work is started by Vijay?

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?