8 machines, each working at the same constant rate, together can complete a certain job in 24 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 16 days? Choose the correct answer
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 24 to 16. 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* 8= 
<gadget id="calculator">3/2* 8</gadget>
<output>12</output>
12   So we need   12-8= 
<gadget id="calculator">  12-8</gadget>
<output>4</output>
4 more machines.   Answer : 4
<result>C</result>
8 machines, each working at the same constant rate, together can complete a certain job in 24 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 16 days?