- A10
- B11
- C12
- D13
Step-by-Step Solution
Net rate = 1/15 + 1/20 − 1/30 = (4 + 3 − 2)/60 = 5/60 = 1/12. So time = 12 minutes.
Answer: C) 12
Two pipes can fill a tank in 15 minutes and 20 minutes respectively, while a waste pipe can empty the full tank in 30 minutes. If all three pipes are opened together, in how many minutes will the tank be filled?
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