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【OG20-P167-133题】
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?
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分析A选项
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分析B选项
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分析C选项
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分析D选项
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分析E选项
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预约名师一对一题目解析课程设Machine B的速度为a，则(800/y)*x+ax=800，a=(800（y-x）)/xy，所以Machine B生产800nails需要时间xy/y-x
题目讨论 （2条评论）
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夜晚半透明
总共
800个 x小时 效率800/x
单独a
800个 y小时 效率800/y
单独b
单独b效率=总共效率-单独a效率=800/x - 800/y
时间=总量/效率
单独b 时间=800/（800/x - 800/y）= e选
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2019-05-22 19:49:59
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emily666回复夜晚半透明
谢谢，解释得很清楚
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2020-03-11 17:37:40
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默默
800/x +800/y= 800* [(x+y)/xy]
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2018-04-21 00:09:52
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默默回复默默
800*xy/800(x+y)
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2018-04-21 00:11:09
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默默回复默默
题看错了，是知道联合速度，求单个的，所以选D
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2018-04-21 00:16:42
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