To fill a cistern, pipes A, B and C take 20 minutes, 15 minute and 12 minutes respectively. The time in minutes that the three pipes together will take to fill the cistern is

5

The above chart was obtained after following the details of the question:

Efficiency of A = 3

Efficiency of B = 4

Efficiency of C = 5

Efficiency of A+B+C = 12

Days required by A, B and C together to complete the work: \(\frac{60 }{12 }\) = 5 days