John and David can finish a job together in 6 hours. If John can do the job by himself in 8 hours, what percent of the job does David do?
Choose the correct choice from the following choices.
A) 35%  B) 45%  C) 25%  D) 30%  E) 20%
You can also plug in numbers. For example, Bob and Alice work at a donut factory and make 24 donuts which is the job ( I picked this as a SMART number).   John on his own works  24/8= 
<gadget id="calculator"> 24/8</gadget>
<output>3</output>
3 donuts per hour.   John and David work   24/6= 
<gadget id="calculator">  24/6</gadget>
<output>4</output>
4 donuts per hour so David works 1 donuts/hour   To find out the percentage, David works 1 donuts/hr x 6 hours= 6 donuts per hour.   Therefore 6 donuts/24donuts = 1/4 = 25%   Answer : 25%
<result>C</result>
John and David can finish a job together in 6 hours. If John can do the job by himself in 8 hours, what percent of the job does David do?