Two pipes A and B can fill a tank in 30 hours and 45 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?
Choose the correct choice from the following choices.
A) 18 hours  B) 15 hours  C) 10 hours  D) 12 hours  E) 8 hours
Part filled by 18 hours in 1 hour = 1/30   Part filled by B in 1 hour = 1/45   Part filled by (18 hours+B) in 1 hour = 1/30 + 1/45 = 5/90 = 1/18   Both the pipes together fill the tank in 18 hours   18 hoursnswer is 18 hours
<result>A</result>
Two pipes A and B can fill a tank in 30 hours and 45 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?