A swimming pool holds 540,000 liters of water. The pool has two drainage pipes. When the pool is completely full, the first pipe alone can empty it in 225 minutes, and the second pipe alone can empty it in 150 minutes. When both pipes are draining together, how long does it take them to empty the pool?

There are 810 dishes that need to be rinsed. Keith can rinse them in 135 minutes by himself. It will take his friend Tom 90 minutes to rinse these dishes. How long will it take them if they rinse these 810 dishes together?

Working together, it takes two different sized hoses 40 minutes to fill a small swimming pool. If it takes 60 minutes for the larger hose to fill the swimming pool by itself, how long will it take the smaller hose to fill the pool on its own?

Left on together, the cold and hot water faucets of a certain bathtub take 4 minutes to fill the tub. If it takes the hot water faucet 9 minutes to fill the tub by itself, how long will it take the cold water faucet to fill the tub on its own?

A rowing team rowed 90 miles while going with the current in the same amount of time as it took to row 10 miles going against the current. The rate of the current was 4 miles per hour. Find the rate of the rowing team in still water.