questions on pipe & cistern

problems on pipes and cisterns.

What is inlet and outlet in pipes and cisterns

Filling pipe, if opened alone, takes 5 minutes to fill a cistern. Suddenly, during the course of fillling, the waste pipe (which is of similar size and flow as of fill pipe) is opened for 2 minutes, then the cistern will be filled in

Two pipes can fill a cistern in 3 hours and 4 hours respectively and a waste pipe can empty it in 2 hours. If all the three pipes are kept open, then the cistern will be filled in :

Two pipes can fill a cistern in 28 and 21 hours respectively and an another pipe can empty 30 gallons of water per hour. All the three pipes working together can fill the empty cistern in 84 hours. What is the capacity (in gallons) of the cistern?

One pipe can fill an empty cistern in 4 hours while another can drain the cistern when full in 10 hours. Both the pipes were turned on when the cistern was half-empty. How long will it take for the cistern to be full?