GRE数学考点介绍之算术篇

信息来源:网络  发布时间:2013-04-06
摘  要:

GRE数学考点介绍之算术篇,本文为大家整理算术部分有关GRE数学考点介绍,非常具有参考性,希望可以供大家参考,更好地备考。

关键字:

GRE数学考点介绍,GRE数学考点

  下面小编整理了在考试中一定会考到的算术部分有关GRE数学考点介绍,供大家参考。
 

  GRE数学复习重要考点:Sum of Arithmetic ProGREssion
 

  The sum of n-numbers of an arithmetic proGREssion is given by
 

  S=nx*dn(n-1)/2
 

  where x is the first number and d is the constant increment.
 

  example:
 

  sum of first 10 positive odd numbers:10*1+2*10*9/2=10+90=100
 

  sum of first 10 multiples of 7 starting at 7: 10*7+7*10*9/2=70+315=385
 

  remember:
 

  For a descending AP the constant difference is negative.
 

  AP
 

  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(2*7-7-1)/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*(2*15-15-1)/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*(2*33-33-1)/2=67+32=99.
 

  Remember:
 

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

  上述就是算术部分有关GRE数学考点介绍,希望大家在备考时能够多加留意,更好地准备GRE数学考试,预祝大家取得理想的GRE数学高分。
 

  您可能还关注:

  GRE数学单位转换注意事项

  如何解决GRE数学粗心问题

  新GRE备考前期如何准备

百小侃(雅思 GRE GMAT),留学考试百事通!随时在线答疑,咨询出国留学、出国考试全方位解答,更有写作免费精批改、免费微课!微信号:bailiedu2016,快快添加吧! 百利天下考试
分享到:
  • 北京
  • 成都
  • 大连
  • 合肥
  • 西安
  • 武汉
  • 南京
  • 广州
  • 天津
010-5795-2000

北京总公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:北京市海淀区中关村丹棱街3号 中国电子大厦B座15层

成都分公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:四川省成都市锦江区红星路三段一号 IFS国际金融中心二号办公楼18层1811

大连分公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:大连沙河口区黄河路620号现代服务业总部大厦19层 C2D1

合肥分公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:安徽省合肥市蜀山区长江西路189号之心城写字楼环球中心A座17层1703

西安分公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:陕西省西安市碑林区南关正街88号长安国际中心A座10层1001

武汉分公司

全国统一咨询热线:010-5795-2000 工作时间:周一至周日(8:30-21:30) 地址:武汉市洪山区珞瑜路10号群光二期写字楼34层01-10号
选址中
选址中
选址中

版权所有:北京环球百利教育科技有限公司

Copyright @ 2004-2018 Bailitop Education. All Right Reserved 备案许可证号:京ICP备11003081号 | 京公网安备11010802010640