题库搜索>问题求解PS-13694
During a trip, Francine traveled x percent of the total distance at an average speed of 40 miles per hour and the rest of the distance at an average speed of 60 miles per hour. In terms of x, what was Francine’s average speed for the entire trip?
分析A选项
分析B选项
分析C选项
分析D选项
分析E选项
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设总路程为100，第一段路程为x,第二段为：100-x
总时间为：x/40+(100-x)/60=(200+x)/120
平均速度=总路程/总时间=100/<(200+x)/120>=12000/200+x.
选E
借我借我一双慧眼吧
X%-----40m/h 1-x%--60m/h 一共用的时间是：2/5x+60-3/5x=60-1/5x
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2015-12-03 16:48:11
223228qa回复 借我借我一双慧眼吧
这个思路为什么不行 不懂
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2020-01-31 16:10:38
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问题求解PS
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GWD
题目信息3m9s
平均耗时
84.3%
平均正确率
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