In a manufacturing plant, it takes 48 machines 4 hours of continuous work to fill 8 standard orders. At this rate, how many hours of continuous work by 72 machines are required to fill 12 standard orders?
Choose the correct choice from the following choices:  A) 3  B) 6  C) 8  D) 9  E) 12
the choices give away the answer..   48 machines take 4 hours to fill 8 standard orders..   in next eq we are doubling the machines from 48 to 72, but the work is not doubling(only 1 1/2 times),   = 4*48/72*12/8= 
<gadget id="calculator">4*48/72*12/8</gadget>
<output>4</output>
4   3ns 3
<result>A</result>
In a manufacturing plant, it takes 48 machines 4 hours of continuous work to fill 8 standard orders. At this rate, how many hours of continuous work by 72 machines are required to fill 12 standard orders?