Two pipes can fill a pool in 6 hours and 9 hours, respectively. How long will it take to fill the pool if both pipes are open together?

Category: Math · Difficulty: expert

Hint: Calculate the rate of filling for each pipe and combine.

Answer

3.6 hours

Explanation

Rates: Pipe 1 = 1/6, Pipe 2 = 1/9. Combined rate = 1/6 + 1/9 = 5/18 pools per hour. Time = 1 / (5/18) = 3.6 hours.

This is a expert math riddle — one of the harder riddles here. The answer is 3.6 hours.

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