[讨论]两道百思不得其解的数学题

出自Gmatprep:

1. If the integer n is greater than 1, is n equal to 2?

(1) n has exactly two positive factors.

(2) The difference of any two distinctic factors of n is odd.

Answer: B. Mine is E. Call for help~

2. For a certain set of n number,n>1, is the average(arithmetic mean)equal to the median?

(1) If the n number in the set are listed in increasing order, then the difference between any pair of sucessive number in the set is 2. 

(2)......

Answer: A.  Don't know why.  

如果n是奇数，那么他的因子至少有1，n和另外一个奇书因子，而奇数因子减去1，肯定是偶数；

如果n是偶数，那么他至少有1，2，n这几个因子，而n-2肯定是偶数；

除非n=2，才符合题目所述的条件。

题目就是说的等差数列啊，那他的算术平均数当然等于中值啊