Question

A tap can fill a tank in 24 hrs and out let can empty the full tank in 30 hrs.in how many hours the empty tank will be filled. If both the tap in and out are open how much time it will take to fill the tank

Answer 1

Part of the cistern filled in 1 hour = 1÷24

Part of the cistern emptied in 1 hour = 1÷30

When both the taps are opened simultaneously, part of cistern fill in 1 hour = 1/24-1/30
=5-4/120
=1/120
Hence, the cisatern wil be filled in 120 hours.