Pipes & Cisterns Mcqs

Q.  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?

a. after 12 mins
b. after 9 mins
c. after 8 1/2 mins
d. after 10 mins

ANSWER: See Answer

x/18 + 12/24 = 1

x = 9
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