GMAT/留學申請專業顧問 Donz 之資訊交流園地

  x，a，b 是positive real number,問 a<x<b?
  (1) x<(a+b)/2
  (2) x>根號ab
Solution:

  19.
  Is z equal to the median of the three positive integers x, y, and z ?
  (1) x < y + z
  (2) y = z
  想請問這題 解答我看得懂 他是代數字的
  可是要怎麼代會比較快
  因為我老是覺得我只代幾組數字
  那如果例外的我沒發現 不就死了
  有人可以教一下嗎
  謝

What is the median number of employees assigned per project for the projects at Company Z?
  (1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
  (2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project.

 234. 還有一題ds  a*b〉0?  (1)a-b>0  (2)a+b>0
 
Solution:

f(x) >0, f(x+y) = f(x)f(y) 問f(0)?
Solution:
    f(x) = f(0+x) = f(0)f(x)
    所以 f(0) 很明顯 = 1
    至於為何要說 f(x) > 0 呢?
    一來是為了確認 f(0) = 1 正確
    二來 f(x) = 0 的話 f(0) 可以為任意數

4. [DS] If 500 is the multiple of 100 that is closest to x and 400 is the multiple of 100 closest to y, which multiple of 100 is closest to x+y?
    1) x<500
    2) y<400
Solution:

1.  x+y, x+5y, x-y, 5x-y 四個數任選二，乘積為 x^2-(by)^2，b為整數，求機率
 解: 1/6
Solution:     
      (ax + by)(cx + dy) = (ac)x^2 + (ad + bc)xy + (bd)y^2
                                                       ^^^^^          ^^
                                                           = 0             = 整數
      基本上 每個選擇的 a, b, c, d 都是整數
      所以 b (題目的 b) 為整數是廢話
      ad + bc = 0, 只有兩個組合有可能產生
      (x+5y, 5x-y)   (x+y, x-y)