Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank? Select the correct option.
A) 15 min  B) 20 min  C) 25 min  D) 30 min  E) 12 min
A in 1 min = 1/20   B in 1 min = 1/30   (A+B) in 1 min = 1/12   both pipes fill in =&gt;12 min   ANSW12 minR 12 min
<result>E</result>
Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank?