Question

if 4.5 of a cistern is filled in 1 minute how much more time will be required to fill the rest of it

Answer 1

Time taken to fill the 4/5 part of the cistern = 1 min = 60 seconds

Time taken to fill the whole cistern = 60 * 5/4 = 15 * 5 = 75 seconds

Part of cistern remaining = 1 - 4/5 = 1/5

Time taken to fill the 1/5 part of the cistern = 75/5 = 15 seconds

Hence it will require 15 seconds to fill the remaining part of the cistern

And total time will be 75 seconds or 1 min 15 seconds