A. 10 min
B. 20 min
C. 30 min
D. 40 min
Work done by waste pipe in 1 minute
=1/20−(1/12+1/15)=−1/10
Waste pipe will empty the full cistern in 10 minutes.
Correct Answer: A. 10 min ✔
Last Updated: November 19, 2019
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