Ankit alone can complete a work in 20 days and Sachin alone can complete the same work in half the time taken by Ankit. In how many days can both together complete 35 of the total work?

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?