Pipes A, B and C can fill a cistern in 20 minutes, 15 minutes and 12 minutes respectively. In how many minutes will the three pipes together fill the cistern?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 5
Pipes running together add the parts they fill in one minute.
Part filled in one minute \(\displaystyle =\frac{1}{20}+\frac{1}{15}+\frac{1}{12}=\frac{3+4+5}{60}=\frac{12}{60}=\frac{1}{5}\)
Time for the whole cistern \(=5\) minutes
The three pipes together fill the cistern in 5 minutes.