P and Q agree to complete a project for ₹450. P can complete it alone in 20 days and Q in 40 days. With the assistance of R, they complete the entire work together in 8 days. What is R's share of the payment?

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?