gre数学考试在新gre考试当中增加了一些难度,但是gre考生也不要太紧张,只要把一些gre数学基本概念掌握好,解题时就一定能轻松应对。3 i( ?% @! `% |9 z
排列组合
9 m) ]5 ~2 l& P4 p H" t2 M 排列数公式和组合数公式:
# t" U3 q n1 ~8 j% g' _ 乘法原理:" `- P# v: w. b# p9 J
一件事的完成可以分成n个步骤,完成其第一步有m1种方法,完成第二步有m2种方法……完成第n步有mn种方法,那么完成这件事一共有N=m1*m2*……*mn种不同的方法。
) r; H- [+ c- u- R 例题.If all of the room numbers in a certain hotel must be even numbers, and if each of the numbers uses all four of the digits 3,4,5 and 8, what is the greatest number of four-digit numbers that the hotel can have?( A8 g' c, `: Q. @: _
例题.What is the total number of different 4-digit integers in which the units’ digit is an odd integer while the thousands’ digit is an even integer?
. h4 o+ f" U+ g- p, M2 B 例题.What is the total number of different 5-digit numbers that contain all of the digits 1,2,3,4, and 5 and/ v u6 f6 @7 L5 U9 Q
1) in which none of the odd digits occur next to each other?: R$ g! ?& l$ b; j
2) in which none of the even digits occur next to each other?
. h" D9 [0 H* K" j4 r" _- t 平时,gre考生一定要注意gre数学基本概念的加强理解,因为无论gre数学考试怎样的题目都是从最基本的概念中演变而来的。 |