How long will it take to fill the tank if both pipes are working?

Question

A tank can be filled by pipe A alone and 22hr by pipe B alone.

Answer 1

If the tank can be filled by pipe A alone in 22 hours and if the tank can be filled by pipe B alone in 22 hours, then the tank could be filled in 11 hours by both pipes working together.

The pipes fill the tank at the same rate, so 2 of the pipes should take half of the time.