标题: [数学] GMAT 数学：if two copying machines... [打印本页] 作者: myice 时间: 2012-9-5 13:57 标题: GMAT 数学：if two copying machines...
if two copying machines work simultaneously at their respective rates, how many copies do they produce in 5 minutes?
(1)one of the machines produce copies at the constant rate of 250 copies per minute.
(2)one of the mechines produce copies at twice the constant rate of the other machine.
这题选E？ 为什么？（1）+（2）不是能搞定么
GMAT培训讲师 robert详细解答回复可见： 这是一个trick。
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