Problem Solving
试题详情
题目：
Working simultaneously at their respective constant rates, Machines A and B produce 800 nails in x hours. Working alone at its constant rate, Machine A produces 800 nails in y hours. In terms of x and y, how many hours does it take Machine B, working alone at its constant rate, to produce 800 nails?
选项:
A、 $$\frac{x}{x+y}$$
B、 $$\frac{y}{x+y}$$
C、 $$\frac{xy}{x+y}$$
D、 $$\frac{xy}{x-y}$$
E、 $$\frac{xy}{y-x}$$
答案:
E
