Question

Pipes Aand B fill a tank in 20 mins and 30 mins respectively,while C can empty it in 25 mins (starting with A, then B and finally C in that order). If each pipe is opened exactly one minute each, then the tank will be filled in?
1) 66mins 56 sec
2) 64 mins 36 sec
3) 63 mins 18 sec​

Answer 1

Answer:

167 minutes

Step-by-step explanation:

Three pipes, A, B, and C are attached to a tank. A and B can fill it in 20 and 30 minutes respectively while C can empty it in 15 minutes.If A, B & C are kept open successively for 1 minute each, how soon will the tank be filled?

Part of tank filled by A in 1 minute= 1/20

Part of tank filled by B in the 2nd minute= 1/30

Part of tank filled in first 2 minutes

= 1/20 + 1/30 = 5/60=1/12

Part of tank emptied by C in the third minute = 1/15.

Part of tank filled in 3 minutes

= 1/12 - 1/15 = 1/60

Time taken to fill 1/60 part = 3 min

Time taken to fill11/12 part

={3(11/12)}/(1/60)= 3×11×60/12= 165 min

The remaining 1/12 can be filled by both A and B successively in 2 min.

So total time taken to fill the tank= 165+2 = 167 min.

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