A hose with a larger diameter working alone can fill a swimming pool in 9 hours. A hose with a smaller diameter working alone can fill a swimming pool in 18 hours. Working together, how long would it take the two hoses to fill the swimming pool?

- The rate of the hose with the large diameter is:   Answer: A). 1/9. - What is the unknown in the problem?   Answer: C). the time it takes for the hoses working together to fill the pool -What part of the job does the hose with the large diameter do?   Answer: B). x/9