A medium water hose can fill a pool in 30 minutes. A larger water hose can fill the same pool in 20 minutes. If both hoses are turned on at the same time, how long will it take to fill the pool? | What equation can be used to solve this work problem? | How many minutes will it take both hoses to fill the pool?

In t minutes, the medium hose fills t/30 of the pool, and the larger hose fills t/20. Together they fill one whole pool, so the equation is t/30 + t/20 = 1. Solving gives 2t/60 + 3t/60 = 1, so 5t = 60 and t = 12 minutes. Thus, choice D is the equation, and both hoses fill the pool in 12 minutes.

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