If pipe A can fill the tank in 45 minutes and pipe B in 30 minutes, find the time to fill the tank if both the pipes are opened together. Select:  A) 12 minutes  B) 20 minutes  C) 18 minutes  D) 15 minutes  E) None of these
Explanation:   In 1 minute pipe A can fill 1/45th part of the tank and pipe B can fill 1/30th part of the tank. If they are opened simultaneously then in 1 minute they can fill (1/45   + 1/30) part of the tank = 1/18th part of the tank.   Hence, in 18 minutes the tank gets filled if pipes A &amp; B are opened together.   ANSWER 18 minutes
<result>C</result>
If pipe A can fill the tank in 45 minutes and pipe B in 30 minutes, find the time to fill the tank if both the pipes are opened together.