Q6:
If two copying machines work simultaneously at their respective constant rates, how many copies do they produce in 5 minutes?
(1) One of the machines produces copies at the constant rate of 250 copies per minute.
(2) One of the machines produces copies at twice the constant rate of the other machine.
答案为什么是E呢？我觉得1和2结合起来就可以知道两者的速度和，再乘上时间不就可以得结果了吗?
有人说，因为2）没有说清楚谁是谁的两倍。
题上不是说的很清楚吗One of the machines produces copies at twice the constant rate of the other machine. | 
