Machine C takes 2 more hours than machine B to make 20 widgets. If working together, the machines can make 25 widgets in 3 hours, how long will it take machine C to make 40 widgets? Choose the correct choice from the following:
A) 5 B) 6 C) 8 D) 10 E) 12
i approached this one by plugging in numbers...started with C.   if 40 are made in 8 hours, then 20 are made in 4 hours. so time of C is 4, and time of B is 2.   rate together: 20/4 + 20/2 = 5+10= 
<gadget id="calculator">5+10</gadget>
<output>15</output>
15. so in 1 hour, together make 15 widgets. in 3 hours= 45. way too much. we can eliminate right away C, B, and A - because B and C reduces the time - the total # of widgets made will be even higher.   now between D and E -&gt; try only one ..if it doesn't work, then the other one is the answer.   i picked E:   12h to make 40 widgets, and 6 hours to make 20. this is the time of C. time of B=4 hours.   20/6 + 20/4 = 10/3 + 20/4   find LCM of 3 and 4 = 12. multiply first by 4, and second by 3:   40+60/12 = 100/12   divide by 4:   25/3   so this is the rate given.   12 is the correct answer
<result>E</result>
Machine C takes 2 more hours than machine B to make 20 widgets. If working together, the machines can make 25 widgets in 3 hours, how long will it take machine C to make 40 widgets?