Re: [討論]問兩題數學

看板GRE (GRE入學考試)作者 (北極狐)時間18年前 (2006/10/26 23:28), 編輯推噓0(000)
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※ 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 the sum of the greatest and 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 = (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: 125.225.96.2 ※ 編輯: foxiness 來自: 125.225.97.58 (10/27 16:32) ※ 編輯: foxiness 來自: 125.225.97.58 (10/27 16:33)
文章代碼(AID): #15GDGPkm (GRE)
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文章代碼(AID): #15GDGPkm (GRE)