- A20 min
- B40 min
- C10 min
- D18 min
Step-by-Step Solution
Net emptying rate = per minute. Half the cistern: min. (40 min is for a full cistern.)
Answer: A) 20 min
A cistern is half full. Pipe A can fill it in 10 minutes and pipe B can empty it in 8 minutes. If both are opened, how long until the cistern is empty?
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