Twelve machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days?	Choices
A) 2
B) 3
C) 4
D) 6
E) 8
Another solution which is faster is Since each machine works at a constant rate. The time needs to bought down from 12 to 8. So the new time is 2/3 of the original time. Thus to achieve this we need the rate to be 3/2 of original.   So 3/2*12= 
<gadget id="calculator">3/2*12</gadget>
<output>18</output>
18   So we need   18-12= 
<gadget id="calculator">  18-12</gadget>
<output>6</output>
6 more machines.   Answer : 6
<result>D</result>
Twelve machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days?