1、 智 課 網 G R E 備 考 資 料 新GRE數學重要考點解析之平均數-智課教育旗下智課教 育新GRE數學重要考點解析,本文就平均數有關的新GRE數學重要考 點做解析,希望可以供考生參考,更好地準備GRE考試,并最終取得理 想的考生成績。本文就平均數有關的GRE數學考試重點做解析,希望可以幫助大家 鞏固基礎,更好地備考GRE數學。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