In a manufacturing plant, it takes 36 machines 8 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?
Select.
A) 3 B) 6 C) 8 D) 9 E) 12
the choices give away the answer..   36 machines take 4 hours to fill 8 standard orders..   in next eq we aredoubling the machines from 36 to 72, but thework is not doubling(only 1 1/2 times), = 8*36/72*12/8= 
<gadget id="calculator">8*36/72*12/8</gadget>
<output>6</output>
6   Ans 6
<result>B</result>
In a manufacturing plant, it takes 36 machines 8 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?