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GRE考試技巧關(guān)于數學(xué)重要考點(diǎn)AP介紹
新GRE考試技巧：數學(xué)重要考點(diǎn)AP
新gre考試實(shí)施以來(lái)，不僅對寫(xiě)作部分茫然不知所措，就連我們所擅長(cháng)的數學(xué)也甚是擔憂(yōu)，相信這其中的原因還是由于考生在新gre數學(xué)復習時(shí)沒(méi)有把基礎打牢。如果新版gre數學(xué)基本考點(diǎn)都沒(méi)有復習到，如何能拿到分數呢?所以說(shuō)，想要新版gre數學(xué)考好，復習的時(shí)候一定要把基本概念和重要考點(diǎn)都弄扎實(shí)。 天針對新版gre數學(xué)復習，小編給大家整理的是關(guān)于平均數的相關(guān)內容，這些概念在考試中一定會(huì )考到的。希望考生能再接再厲，取得一個(gè)好成績(jì)，突破新版gre數學(xué)難的困境。
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.
由于美國數學(xué)基礎教育的難度增加導致數學(xué)考試越來(lái)越難，但新gre數學(xué)復習考點(diǎn)都是高中時(shí)候學(xué)到的知識點(diǎn)，考生不要過(guò)于緊張，把基本概念弄明白，再記住一些新版gre數學(xué)必備的詞匯，那么相信新版gre數學(xué)應該沒(méi)有問(wèn)題。
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