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新GRE数学重要考点 平均数
日期:2013-12-19 17:00

(单词翻译:单击)

 下面为大家介绍GRE数学平均数考点。如果新GRE数学考点都没有复习到,如何能拿到满意的GRE数学分数呢?所以说,想要新GRE数学考好,复习的时候一定要把新GRE数学考点弄扎实。
  Average of n numbers of arithmetic progression (AP) is the average of the smallest and the largest number of them. The average of m number can also be written as x + d(m-1)/2.
  Example:
  The average of all integers from 1 to 5 is (1+5)/2=3
  The average of all odd numbers from 3 to 3135 is (3+3135)/2=1569
  The average of all multiples of 7 from 14 to 126 is (14+126)/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(m-1)/2,and the n-th number is s/m + d(2n-m-1)/2.
  Example:
  if the sum of 7 consecutive even numbers is 70, then the first number x = 70/7 - 2(7-1)/2 = 10 - 6 = 4.
  the last number (n=m=7)is 70/7+2(27-7-1)/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+(n-1)
  AP:numbers from average
  all m numbers of an AP can be calculated from the average. the first number x = c-d(m-1)/2, and the n-th number is c+d(2n-m-1)/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(15-1)/2=20-7=13 and the last number (n=m=15) is 20+1(215-15-1)/2=20+7=27.
  if the average of 33 consecutive odd numbers is 67, then the first number x=67-2(33-1)/2=67-32=35 and the last number (n=m=33) is 67+2(233-33-1)/2=67+32=99.
  Remember:
  sum of the m numbers is cm,where c is the average.
  以上就是新GRE数学平均数考点的介绍。考生不要过于紧张,把基本概念弄明白,再记住一些新GRE数学必备的词汇,那么相信新GRE数学应该没有问题。由于美国数学基础教育的难度增加导致新GRE数学越来越难,但GRE数学考点都是高中时候学到的知识点。

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重点单词
  • incrementn. 增加(增加物,增量,余差)
  • calculatedadj. 计算出的;适合的;有计划的 v. 计算;估计;
  • constantadj. 经常的,不变的 n. 常数,恒量
  • calculatev. 计算,估计,核算,计划,认为
  • formulan. 公式,配方,规则;代乳品 adj. (赛车的)级的