Arithmetic Aptitude :: Pipes & Cistern
4. Two pipes A and B can fill a tank in 9 hours and 3 hours respectively. If they are opened on alternate hours and if pipe A is opened first, in how many hours will the tank be full?
Tank part filled by pipe A in 1 hour =1/9
Tank part filled by pipe B in 1 hour =1/3
Given Pipe A and B are opened alternatively.
So Part filled in every 2 hours =(1/9+1/3)=4/9
Tank Part will be filled in 4 hour =2*4/9=8/9
Remaining part = (1-8/9)=1/9
So next is A turn.
So Pipe A will fill remaining 1/9 part in next 1 hour.
Total Time = (4 hrs + 1 hrs) = 5 hrs.