8 identical machines, working alone and at their constant rates, take 6 hours to complete a job lot. How long would it take for 12 such machines to perform the same job?  Choose the correct choice
A) 6 hours B) 8.75 hours C) 12 hours D) 4 hours E) 16 hours
Let each machine do 1 unit of work for 1 hour   8 machines --&gt; 8 units of work in 1 hour   For 6 hours = 8*6= 
<gadget id="calculator">8*6</gadget>
<output>48</output>
48 Units of total work is done.   Now this 48 Units of total work must be done by 3 machines   12 units of work(12 machines) ---&gt; 1 hour   for 48 Units of work   12*4 ---&gt; 1*4 hours   4 hours 4 hours
<result>D</result>
8 identical machines, working alone and at their constant rates, take 6 hours to complete a job lot. How long would it take for 12 such machines to perform the same job?