Re: [計量] 好多題計量請教

看板GRE (GRE入學考試)作者Daniel19 (小美)時間15年前 (2011/01/15 22:34)推噓2(2推 0噓 3→)

留言5則, 3人參與討論串11/26 (看更多)

※ 引述《balance9235 (退伍變米蟲)》之銘言： : 1. A rectangular solid has a volume of 30, and its edges have integer lengths. : What is the greatest possible surface area of this solid? : (A) 82 : (B) 86 : (C) 94 : (D) 122 : (E) 180 ANS:(D) 我算1.3.10表面積94 因為沒有規定三邊一定要不等長，所以是1,1,30 (30+30+1)x2 = 122 : 2. Which of the following is the second power of sqrt(1+√1) : (A) 1 : (B) √2 : (C) 2 : (D) 4 : (E) 1+√2 ANS:(C) 我算1+√1 1+√1 = 2 : 3. In the xy-plane, line l passes through the origin and is perpendicular to : the line 4x + y = k, where k is a constant. If the two lines intersect at : the same point (t, t+1), what is the value of t? : (A) 4/3 : (B) 5/4 : (C) 3/4 : (D) -5/4 : (E) -4/3 ANS:(E) 因為垂直又經過原點，所以那條線會是 4y - x = 0 把點帶進去(t,t+1) 得到t+4-4t=0 所以t=-4/3 : 4. A bag contains red gloves, black gloves, ans white ones. What is the LEAST : number of gloves that must be taken out of the bag to be sure of having : 4 pairs of gloves? : (A) 6 : (B) 8 : (C) 9 : (D) 10 : (E) 12 ANS:(D) 原本有幾雙也不知道.... 這題要考慮最糟狀況，你最慘就是全部四雙都來自同個顏色，另外兩種顏色各一 1+1+8=10 : 5. Each of the following numbers has one digit blotted out. Which of the : numbers CANNOT be a sum of two consecutive odd integers? : (A) 2,□24 : (B) 3,□32 : (C) 4,□44 : (D) 5,□54 : (E) 6,□68 ANS:(D) 不知道怎麼判斷假設兩個連續的奇數是2k+1,2k+3 所以加起來是4k+4一定可以被四整除檢查之後你發現只有D無法 : 6. If p, q, r represent different positive integers, and pqr = 2009, what is : the greatest result of p + q + r? : (A) 49 : (B) 55 : (C) 91 : (D) 295 : (E) 2011 ANS:(D) 這題有陷阱，在p,q,r是不同的正整數所以你把2009分解之後得到2009=7*7*41 所以你就取個p=1,q=7,r=287 反正妳就是要讓比較大的出現就對了 : 7. If two cards are drawn drom a deck without replacement, the probability : that both are aces is : (A) 1/26 : (B) 7/52 : (C) 16/2652 : (D) 12/2652 : (E) 12/103 ANS:(D) 我的式子列 (C4取2*C13取1)/C52取2 你的分子多了C13取1，因為不是每一個數字都在你的考慮範圍內多這個就多考慮了兩張2,3,4,5.....Q : 8. In the xy-plane, the coordinates of △ABC are (0,0), (4,1) and (2,4), : respectively. What is the area of △ABC? : (A) 4 : (B) 5 : (C) 6 : (D) 7 : (E) 8 ANS:(D) 邊長有根號不知道怎麼用三邊長求面積這題有很多種辦法做，可以用向量作，也可以用行列式作如果用行列式作的話是這樣的，把所有點列一列交叉相乘(右斜乘完加起來減掉左斜相乘相加)就可以了 |0 4 2 0| 面積=1/2 | | = 7 |0 1 4 0| : 9. In the xy-plane, O is the center of circle with coordinate (m,4), and a : point (m,-1) is on the circle. : Column A Column B : The circumference 32 : of circle O. ANS:B 因為圓心在(M,4)又經過(M,-1)所以知道半徑是5，圓周就是5*2*PI大概是31.4.. 小於32所以選B : 10. At the corporate headquarters of a large enterprise, outside each office : there is a keyboard, on which there are two letters, A and B, and digits : from 0 to 9, inclusive. To gain entrance to an office, an employee must : punch in an access code. If a code consists of the letter A or B followed : by either 2 or 3 different digits, how many different access codes are : there? : (A) 2,200 : (B) 2,000 : (C) 1,620 : (D) 1,560 : (E) 1,440 ANS:(C) C2取1*C10取2 + C2取1*C10取3不對因為數字有先後的差異，所以不可以用C取 C2取1*10*9+C2取1*10*9*8=1620 : 今天題目比較少，一樣要麻煩大家了！ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.43.102.240 ※ 編輯: Daniel19 來自: 114.43.102.240 (01/15 22:36)