Re: [討論]問兩題數學

看板GRE (GRE入學考試)作者 (原諒我的無能為力)時間18年前 (2006/10/27 00:25), 編輯推噓2(202)
留言4則, 3人參與, 最新討論串3/3 (看更多)
※ 引述《foxiness (北極狐)》之銘言: : ※ 引述《CSL (原諒我的無能為力)》之銘言: : : 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一樣大 : : 謝謝!! : 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 : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 不好意思我資質駑鈍..可以解釋或說明一下這個式子怎麼來的嗎? 謝謝!! = (2a + k)/2 : = a + k/2 : (median:偶數個數就是兩個中間數的平均數) : (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:奇數個數就是中間那個數) -- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.134.24.77

10/27 08:34, , 1F
the sum of the greatest and least
10/27 08:34, 1F

10/27 11:20, , 2F
中位數不是中間兩個數的平均嗎?(若為偶數個的話)樓上的為何說갠
10/27 11:20, 2F

10/27 11:21, , 3F
是最大數和最小數的和..不懂><
10/27 11:21, 3F

10/27 16:32, , 4F
抱歉>"<..中文用太習慣了~改不回來~謝謝提醒
10/27 16:32, 4F
文章代碼(AID): #15GE624I (GRE)
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文章代碼(AID): #15GE624I (GRE)