Answer : 2 7 hrs Explanation : Answer: B) 7 hrs Explanation: Given,P can fill in 12 hrsQ can fill in 15 hrsR can fill in 20 hrs=

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Three taps P, Q and R can fill a tank in 12 hrs, 15 hrs and 20 hrs respectively. If P is open all the time and Q and R are open for one hour each alternately, starting with Q, then the tank will be full in how many hours ?