新GRE数学重要考点解析之平均数-智课教育旗下智课教育

1、 智 课 网 G R E 备 考 资 料 新GRE数学重要考点解析之平均数-智课教育旗下智课教 育新GRE数学重要考点解析,本文就平均数有关的新GRE数学重要考 点做解析,希望可以供考生参考,更好地准备GRE考试,并最终取得理 想的考生成绩。本文就平均数有关的GRE数学考试重点做解析,希望可以帮助大家 巩固基础,更好地备考GRE数学。Average of n numbers of arithmetic progression (AP is the average of the smallest and the largest number of them. The average of m n

2、umber can also be written as x + d(m-1/2.Example:The average of all integers from 1 to 5 is (1+5/2=3The average of all odd numbers from 3 to 3135 is(3+3135/2=1569The average of all multiples of 7 from 14 to 126 is(14+126/2=70remember:Make sure no number is missing in the middle.With more numbers, av

3、erage of an ascending AP increases. With more numbers, average of a descending AP decreases. AP:numbers from sumgiven 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

4、-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=7is 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

5、 n-th number: x+(n-1AP:numbers from averageall 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 isc+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 t