Pipe A fills a tank in 20 hours and pipe B in 30 hours. If both are opened together, how long do they take to fill the empty tank?
Answer and explanation
Correct answer: A. 12 hours
- Step 1: Rate of A + rate of B = 1/20 + 1/30 = 1/12 of the tank per hour.
- Step 2: Time = 12 hours.
Answer
12 hours.
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