Working simultaneously and independently at an identical constant rate, 20 machines of a certain type can produce a total of x units of product P in 4 days. How many of these machines, working simultaneously and independently at this constant rate, can produce a total of 3x units of product P in 8 days?	Options.
A) 30  B) 32  C) 35  D) 38  E) 40
The rate of 20 machines is rate=job/time=x/4 units per day --&gt; the rate of 1 machine 1/20*(x/4)=x/80 units per day;   Now, again as {time}*{combined rate}={job done}   then 8*(m*x/80)=3x --&gt; m=30.   30nswer: 30.
<result>A</result>
Working simultaneously and independently at an identical constant rate, 20 machines of a certain type can produce a total of x units of product P in 4 days. How many of these machines, working simultaneously and independently at this constant rate, can produce a total of 3x units of product P in 8 days?