题库搜索>问题求解PS-13695
Each of the 30 boxes in a certain shipment with either 10 pounds or 20 pounds, and the average (arithmetic mean) weight of the boxes in the shipment is 18 pounds. If the average weight of the boxes in the shipment is to be reduced to 14 pounds by removing some of the 20-pound boxes, how many 20-pound boxes must be removed?
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设 10pound X个， 那么 20pound 30-X 个
（10X+ (30-X)*20）/30=18 X=6
20poind: 24个
[10*6 +20*（24-n)]/ (30-n)=14
n=20
441666bo
题不难，但是至少得话3到4分钟来算
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2022-11-26 15:13:30
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问题求解PS
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