A large tanker can be filled by two pipes A and B in 60 and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half? Choose the correct choice from the following answers: A) 15 min B) 20 min C) 27.5 min D) 30 min E) 25 min
Part filled by (A + B) in 1 minute = (1/60 + 1/40) = 1/24   Suppose the tank is filled in x minutes.   Then, x/2(1/24 + 1/40) = 1   x/2 * 1/15 = 1 =&gt; x = 30 min   ANSWER:30 min
<result>D</result>
A large tanker can be filled by two pipes A and B in 60 and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half?