Working alone, machine X can manufacture 1,000 nails in 15 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?
Answers:
A) 3 9/17	B) 5 1/3	C) 7	D) 7 1/2	E) 8 4/7
rate of machine x = 1000/15   (1000/15 + y)5=1000   y=200-200/3=400/3   400/3 * t = 1000   t=7 1/2   D. 7 1/2
<result>D</result>
Working alone, machine X can manufacture 1,000 nails in 15 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?