दो पाइप P और Q एक टैंक को क्रमशः 24 घंटे और 32 घंटे में भर सकते हैं। यदि दोनों पाइपों को एक साथ खोल दिया जाता है, तो पहले पाइप P को कितने घंटे बाद बंद किया जाना चाहिए ताकि टैंक ठीक 28 घंटे में पूरी तरह भर जाए?

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?