X लड़के किसी कार्य को 80 दिनों में पूरा कर सकते हैं। उसी कार्य का आधा भाग 2X लड़के कितने समय में पूरा करेंगे?

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?