Question
Pipe βAβ and pipe βBβ can fill a cistern in 20
minutes and 15 minutes respectively. Pipe βCβ alone can empty the cistern in 10 minutes. If all three pipes are opened together then what is the time taken to fill 25% of the cistern? ty-sscSolution
Let the capacity of the cistern = 60 units Then, efficiency of pipe βAβ = 60/20 = 3 units/minute Efficiency of pipe βBβ = 60/15 = 4 units/minute Efficiency of pipe βCβ = 60/10 = 6 units/minute So, combined efficiency of pipes βAβ, βBβ and βCβ = 3 + 4 β 6 = 1 units/minute 25% of the cisternβs capacity = 15 units Therefore, time taken by all 3 pipes together to fill 25% of the cistern = 15/1 = 15 minutes
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