नल A एक टंकी को 206 घंटे में भर सकता है जबकि नल B इसे 309 घंटे में खाली कर सकता है। यदि A और B दोनों को एक साथ खोल दिया जाए, तो टंकी कितने घंटों में भर जाएगी?

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?