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标题: prep数学ps题 [打印本页]

作者: zhongyaya    时间: 2010-9-24 08:49     标题: prep数学ps题

Working alone at its own constant rate, a machine seals k cartons in 8 hours, and working alone at its own constant rate, a second machine seals k cartons in 4 hours.If the two machines, each working at its own constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?

题目问的问题不太明白什么意思
作者: liexodus    时间: 2010-9-25 06:48

就是问两个一起做,在同样的时间里,快的那个完成了总的工作量的百分之几。
你可以列个等式来的,设完成A工作量,时间T
T(K/8+k/4)=A

T=8A/3K

所以快的那个在时间T里面就是完成了8A/3K×K/4=2/3A
作者: liexodus    时间: 2010-9-26 06:48

这种题可能就是这种思维。




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