Pipe P can fill a tank in 2 hours, pipe Q in 4 hours and pipe R in 12 hours. If all the pipes are open, in how many hours will the tank be filled?  Pick one:  A) 2 hours  B) 1.2 hours  C) 3 hours  D) 1.5 hours  E) 2.5 hours
Explanation:   Part filled by (P + Q + R) in 1 hour = (1/2 + 1/4 + 1/12) = 5/6   All the three pipes together will fill the tank = 6/5= 
<gadget id="calculator">6/5</gadget>
<output>6/5 = around 1.2</output>
1.2 hours   ANSWER 1.2 hours
<result>B</result>
Pipe P can fill a tank in 2 hours, pipe Q in 4 hours and pipe R in 12 hours. If all the pipes are open, in how many hours will the tank be filled?