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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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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 (4条评论)

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180687pkqh
1/A+1/B=1/x 1/y+1/B=1/x 1/B=(y-x)/xy B=xy/(y-x)
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0 回复 2022-03-30 11:31:40
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emily666
这道题我终于可以秒做了
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0 回复 2020-06-01 16:10:07
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568588kopd回复emily666
记住答案了
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0 回复 2022-01-09 19:17:56
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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5
0 回复 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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1 回复 2020-03-11 17:37:40
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默默
800/x +800/y= 800* [(x+y)/xy]
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0 回复 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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0 回复 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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1 回复 2018-04-21 00:16:42
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