यदि 72 व्यक्ति 6 दिनों में 220 मीटर लंबी दीवार बनाते हैं, तो 5 दिनों में उसी प्रकार की 550 मीटर लंबी दीवार बनाने के लिए कितने व्यक्तियों की आवश्यकता होगी?

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?