标题: add maths 求助 [打印本页] 作者: paopaoyuu 时间: 2012-11-10 10:28 AM 标题: add maths 求助 permutation and combination:
1) how many ways can 5 fruits be chosen from 6 different apples and 4 different oranges given that 3 apples must be chosen?
我的答案：6C3 X 4C2 = 120
书本给的答案：10C5 X 6C3 = 5040
为什么是10叻？为什么要加起来？
2) calculate the number of arrangements of the letters of the the word "INCLUDE" if all consonants are together.
我的答案：4P4 X 4P3 = 576
书本给的答案：4P4 X 4P4 = 576
虽然答案一样，可是算法不一样~作者: CrimsonL. 时间: 2012-11-10 11:30 AM 本帖最后由 CrimsonL. 于 2012-11-10 11:43 AM 编辑