pipes P and Q would fill a cistern 18 and 24 minutes respectively. Both pipes being opened, find when the first pipe must be turned off so that the cistern may be just filled in 12 minutes? December 30, 2021December 30, 2021 administrator A. after 12 minsB. after 9 minsC. after 8 1/2 minsD. after 10 minsCheck AnswerB. after 9 mins Share the PostRelated Posts:A tank is filled by three pipes with uniform flow.…A pipe can fill a cistern in 20 minutes whereas the…A cistern has a leak which would empty the cistern…One pipe can fill a tank three times as fast as…A cistern has three pipes, A, B and C. The pipes A…Pipes A and B can fill a tank in 5 and 6 hours…