Anjali and Pranjali can paint a house in 10 days and 15 days respectively. If they work on alternate days starting with Pranjali on the first day, in how many days will the house be completely painted?

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?