GMAT/留學申請專業顧問 Donz 之資訊交流園地

  139.z>y>x>1,x,y,z都是質數
  1.y=x+2
  2.z=x+4
Solution:
  同意 (B) 因為除了 3,5,7 之外
  沒有三個連續質數 最大和最小差距為 4
  我們來檢驗大於 10 的奇數好了
  個位數必定為 1,3,5,7,9
  如果任何三個奇數排在一起 一定有一個為 3 的倍數
  假設連續三個奇數是 n. n+2, n+4 (n > 10)
  不管 n = 3K, 3K+1, 3K+2
  都會有其中一個是 3 的倍數囉
  所以就只有 3 可以為 3 的倍數 又是質數
  (就是 3 本身啦)

  <V2> DS：問n除以10的時候的餘數是多少
  （1）n除以5的時候的餘數是2
  （2）n除以2的時候的餘數是1（貌似是1）
 

Is n odd?
 
(1) n is divisible by 3
(2) 2n is divisible by twice as many positive integers as n

128.
A school administrator will assign each student in a group of n students to
one of m classrooms. If 3<m<13<n, is it possible to assign each of the n stu\
dents to
one of the m classrooms so that each classroom has the same number of studen\
ts assigned
to it?
     題目就是問 n/m is an integer? (m 是否可以整除 n)
 1)  It is possible to assign each of 3n students to one of m classrooms so
 that each classroom has the same number of students assigned to it.

For a
nonnegative integer n, if the remainder is 1 when 2ⁿ
is divided by 3, then which of the following must be true?

  If r and s are positive integers, is r/s   an integer?
  (1)  Every factor of s is also a factor of r.
  (2)  Every prime factor of s is also a prime factor of r.
Solution: