Re: [計量] 麻煩各位 ^^

看板GRE (GRE入學考試)作者Merica (美加文教)時間14年前 (2011/06/15 10:26)推噓0(0推 0噓 0→)

留言0則, 0人參與討論串3/3 (看更多)

※ 引述《collings0628 (collings)》之銘言： : How many two-digit positive integers N have the peoperty that the sum of N and : the number obtained by reversing the order of the digits of N is a perfect : square? (A)4 (B)5 (C)6 (D)7 (E)8 Ans:E 假設2位數N = ab, a, b為不是0的digits. (10a+b) + (10b+a) = R^2 11a+11B = R^2 11(a+b) = R^2 a+b = 11 所以N = 29, 38, 47, 56, 65, 74, 83, 92共8個 : Eight light bulbs numbered 1 through 8 are arranged in a circle. The bulbs are : wired so that every third bulb, counting in a clockwise direction, flashes : until all bulbs have flashed once. If the bulb numbered 1 flashes first, : which numbered bulb will flashed last? (A)2 (B)3 (C)4 (D)6 (E)7 Ans:D 1～8依順時針方向排成一圈，1先亮，然後依順時針方向每第三個會發亮，則依序亮的是4, 7, 2, 5, 8, 3, 6 : If y不等於3 and 3x/y is a prime integer greater than 2, which of the following : must be ture? : I. x=y : II. y=1 : III. x and y are prime integers. : Ans: None 3x/y = 3, 5, 7, 11, …… 3x = 3y，3x = 5y，3x = 7y，…… 以3x = 5y為例，x = 10, y = 6，x = 15, y = 9，x = 20, y = 12 由這些例子可看出I, II, III都不一定成立 : In the xy-plane, if the equation of the line K is ax^2 + bx + c =0, which of : the following must be ture? : I. If a is postive, the x-intercept is postive. : II. If b is postive, the slop is postive. : III. If a and b are negative, the slop is negative. : Ans: III only 為什麼I不行@@ x-intercept是在y = 0時x的數值，即ax^2 + bx + c = 0時x之數值 x = -b±√b^2-4ac／2a，假設a = 1, b = 4, c = 3， x^ + 4x + 3 = 0，x = -3, -1， x-intercept為-3, -1，皆非正，故I不一定對 : 比大小 : 條件: The sum of seven integers is -1. : Column A: The maximum number of the seven integers that can be large than 13 : Column B: 6 : Ans:C 不知是不是我會錯意,求不出C這答案 Column A意為〝這7個整數中，最多有幾個其數值可以>13〞，因為7個整數總和為-1，故頂多6個數>13，至少要有一數是負值，才能總和 = -1，因此答案(C) : A bus trip of 450 miles would have taken 1 hour less if the average speed S of : the trip had been greater by 5 miles per hour. : Column A: The average speed S, in miles per hour, for the trip : Column B: 50 : Ans: B 題目給的條件似乎怪怪的? 設S是時數 450/S+5 – 450/S = 1 可算出　S^2 + 5S + 2250 = 0 (S+50) (S-45) = 0 S = 45, -50(不合) 所以答案(B) (以上內容由美加黃冠文老師提供) -- ▅▅▅▅ ▅▅ ▅▅▅ ▅ ▅▅ ▅▅▅ █ █ █ █▅ █▄█ ▄ █ █▄█ █ █ █ █▄ █◥▅ █ █▅ █ █ 7/2(六)下午2：00美加文教新制GRE&字彙三合一免費講座莫清崴博士/江璞教授主講歡迎蒞臨 http://www.merica.com.tw/event/20110702/ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.36.53.186