Pipe A can fill the tank in 30 minutes and pipe b can empty the tank in 90 minutes. How long it will take to fill the tank if both pipes are operating together?
Choose the correct choice from the following: A) 30 B) 35 C) 40 D) 45 E) 50
Pipe A fills 1/30th of the tank in a minute and pipe B empties 1/90th of the tank   (1/30)-(1/90)=(1/x)   2/90=1/x =&gt; x=45   Answer: 45
<result>D</result>
Pipe A can fill the tank in 30 minutes and pipe b can empty the tank in 90 minutes. How long it will take to fill the tank if both pipes are operating together?