Question

Two taps can separately fill a cistern 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 18 minutes. the waste pipe can empty the full cistern in?

Answer 1

heya your answer is heye

☆Work done by third tap in 1 min = (1/18-1/10+1/15) = -10/90 = -1/9 (The negative value denote that emptying)
so the third tap alone can empty the cistern in 9 min.☆