作者CSL (原谅我的无能为力)
看板GRE_Verbal
标题Re: [讨论]问两题数学
时间Fri Oct 27 00:27:45 2006
※ 引述《foxiness (北极狐)》之铭言：
: ※ 引述《CSL (原谅我的无能为力)》之铭言：
: : 1.If y is the average(arithmetic mean) of
: : n consecutive positive integers, n>1
: : what is the sum of the greatest and least of
: : these integers?
: : 答案是2y
: n consecutive positive integers:
: a, a+1, a+2, a+3,....,a+k (n = k+1)
: y = ( a + a+1 + a+2 + a+3 + ... + a+k ) / (k+1)
: = ( a(k+1) + k(1+k)/2) / (k+1)
: = a + k/2
: greatest + least = a + a + k = 2a + k = 2(a+k/2) = 2y
: : 2. S is a set of n consecutive integers
: : The mean of S The median of S
: : 答案是C一样大
: : 谢谢!!
: n consecutive positive integers:
: a, a+1, a+2, a+3,....,a+k (n = k+1)
: (1) Assume k = odd n = k+1 = even
: The mean of S = ( a + a+1 + a+2 + a+3 + ... + a+k ) / (k+1)
: = a + k/2
: The median of S = ((a+(k-1)/2) + (a+(k+1)/2)) /2
: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
不好意思我资质驽钝..可以解释或说明一下这个式子怎麽来的吗?
谢谢!!
= (2a + k)/2
: = a + k/2
: (median:偶数个数就是两个中间数的平均数)
: (2) Asuume k = even n = k+1 = odd
: The mean of S = ( a + a+1 + a+2 + a+3 + ... + a+k ) / (k+1)
: = a + k/2
: The median of S = a + k/2
: (median:奇数个数就是中间那个数)
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◆ From: 220.134.24.77
1F：推 daadaa:the sum of the greatest and least 10/27 08:34
2F：推 CSL:中位数不是中间两个数的平均吗?(若为偶数个的话)楼上的为何说갠 10/27 11:20
3F：→ CSL:是最大数和最小数的和..不懂>< 10/27 11:21
4F：→ foxiness:抱歉>"<..中文用太习惯了~改不回来~谢谢提醒 10/27 16:32