Question

If 4/5 of cistern is filled in 1 minute ,how much time will be required to fill the empty cistern

Answer 1

Solution :
       4/5 th of Cistern is filled in one minute
therefore whole cistern will be filed in 5/4th of minute
                                         = 5/4*60 seconds
                                         =5*15 seconds
                                         = 75 seconds
Hope this helps you!!