補充一道數學思路

2003-02-22 17:11:01

我2.20也有考到下面这题
补充以下这题的题目及解题思路及答案
several pieces of rope, mean(mathematical average) 64cm, median 84cm, the length of the longest rope is 14cm more than four time the length of the shortest rope. What is the length of the longest rope?
题目应该还有一个条件是总共七个数
解法: 设最小数为s,=>最大数l为4s+14,=>除最大最小二数及中位数84外,其合设为A:
方程式如下:
(s+(4s+14)+84+A)/7=68 A=378-5s
用代入法,自答案E开始
E, l=152 ==>4s+14=152 s=34.5 A=205.5
思路, 设A中较小二数=最小数s,将其余除以2看是否会至少大于中位数84,则数列如下
34.5 34.5 34.5 84 68.25 68.25 152 ==> E(x) 因为68.25<84
D,l=134 => 4s+14=134 s=30 A=228
如上,数列如下
30 30 30 84 84 84 134 ==> D(V)
其它选项不记得
　

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