Working alone, machine X can manufacture 1,000 nails in 10 hours. Working together, machines X and Y can manufacture 1,000 nails in 5 hours. How many hours does it take machine Y to manufacture 1,000 nails working alone?  Choose the correct choice
A) 3 9/17  B) 5 1/3  C) 10  D) 11 1/5  E) 18 4/7
rate of machine x = 1000/10   (1000/10 + y)5=1000   y=100   100 * t = 1000   t=10   10.
<result>C</result>
Working alone, machine X can manufacture 1,000 nails in 10 hours. Working together, machines X and Y can manufacture 1,000 nails in 5 hours. How many hours does it take machine Y to manufacture 1,000 nails working alone?