新gre数学重要考点：AP

　　2014新gre考试实施以来，不仅对写作部分茫然不知所措，就连我们所擅长的数学也甚是担忧，相信这其中的原因还是由于考生在新gre数学复习时没有把基础打牢。如果新版gre数学基本考点都没有复习到，如何能拿到分数呢?所以说，想要新版gre数学考好，复习的时候一定要把基本概念和重要考点都弄扎实。

　　天针对新版gre数学复习，小编给大家整理的是关于平均数的相关内容，这些概念在考试中一定会考到的。希望考生能再接再厉，取得一个好成绩，突破新版gre数学难的困境。

　　AP

　　Average of n numbers of arithmetic progression is the average of the smallest and the largest number of them. The average of m number can also be written as x + d/2.

　　Example:

　　The average of all integers from 1 to 5 is /2=3

　　The average of all odd numbers from 3 to 3135 is /2=1569

　　The average of all multiples of 7 from 14 to 126 is /2=70

　　remember:

　　Make sure no number is missing in the middle.

　　With more numbers, average of an ascending AP increases.

　　With more numbers, average of a descending AP decreases.

　　AP:numbers from sum

　　given the sum s of m numbers of an AP with constant increment d, the numbers in the set can be calculated as follows:

　　the first number x = s/m - d/2,and the n-th number is s/m + d/2.

　　Example:

　　if the sum of 7 consecutive even numbers is 70, then the first number x = 70/7 - 2/2 = 10 - 6 = 4.

　　the last number is 70/7+2/2=10+6=16.the set is the even numbers from 4 to 16.

　　Remember:

　　given the first number x, it is easy to calculate other numbers using the formula for n-th number: x+

　　AP:numbers from average

　　all m numbers of an AP can be calculated from the average. the first number x = c-d/2, and the n-th number is c+d/2, where c is the average of m numbers.

　　Example:

　　if the average of 15 consecutive integers is 20, then the first number x=20-1/2=20-7=13 and the last number is 20+1/2=20+7=27.

　　if the average of 33 consecutive odd numbers is 67, then the first number x=67-2/2=67-32=35 and the last number is 67+2/2=67+32=99.

　　Remember:

　　sum of the m numbers is cm,where c is the average.

　　由于美国数学基础教育的难度增加导致数学考试越来越难，但新gre数学复习考点都是高中时候学到的知识点，考生不要过于紧张，把基本概念弄明白，再记住一些新版gre数学必备的词汇，那么相信新版gre数学应该没有问题。