Problem Solving
试题详情
题目：
Working alone at their respective constant rates, machine A and machine B can fill a certain order in 3 hours and 6 hours, respectively. If the two machines work simultaneously at their respective constant rates, how many hours does it take the two machines to fill 1/2 of that order?
选项:
A、1/2
B、3/4
C、1
D、11/4
E、11/2
答案:
C
