向各位大神请教几个数学题，不胜感激~

cathylt

1、For a certain set of n numbers, where n > 1, is the average (arithmetic mean) equal to the median?
(1) If the n numbers in the set are listed in increasing order, then the difference between any pair of successive numbers in the set is 2.
(2) The range of the n numbers in the set is 2(n - 1).

答案是A，如果n是偶数不就不可以了吗，不是很理解哎...

2、If n and m are positive integers, what is the remainder when 3^(4n + 2 + m) is divided by 10 ?
(1) n = 2
(2) m = 1
答案是B

感谢各位了~~~

greengreed

yes, but the remainder might change.

cathylt

恩，灰常感谢啊O(∩_∩)O~
那第二个题中，无论3的多少次方应该个位都不是0，应该都不能被10整除的吧？？

greengreed

1，等差数列的average总是等于median,不管奇数个还是偶数个项， so (1) is sufficient, (2) obvious not sufficient.
2, pls note: 3^4n = (3^4)^n , the last digit is always 1. so don't care about n, know m is enough.