Six machines at a certain factory operate at the same constant rate. If five of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all six machines, operating simultaneously, to fill the same production order?  Choose the correct choice from the following:
A) 3  B) 5  C) 6  D) 16  E) 24
The total work is 5*30= 
<gadget id="calculator">5*30</gadget>
<output>150</output>
150 machine hours   The time required for six machines is  150/6= 
<gadget id="calculator"> 150/6</gadget>
<output>25</output>
25 hours, thus 5 fewer hours.   The answer is 5.
<result>B</result>
Six machines at a certain factory operate at the same constant rate. If five of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all six machines, operating simultaneously, to fill the same production order?