Re: [計量] 還是數學問題...
有錯請指正
※ 引述《alibigking (森大王)》之銘言：
: 排列組合的問題
: 一樣是在gre guide上的practice question
: 1. A teacher prepares a test. She gives 5 objective type questions out of
: which 4 have to be answered. Find the total ways in which they can be
: answered if the first 2 questions have 3 choices and the last 3 have 4
: choices.
: A: 816
五題選四題，所以挑一題不選
分兩種討論
挑題選擇 作答選擇
2 * 3 * 4^3 = 384 (挑前兩題其一)
3 * 3^2 * 4^2 = 432 (挑後三題其一)
合為816
: 2. How many 5 digit numbers are there with distinct digits?
: A: 27216
(這題好像很多人問過...)
因為萬位不能0，有限制，所以從萬位數字開始做
萬 ..... 個
9*9*8*7*6
: 3. How many five digit numbers can be formed using the digits 0,2,3,4 and 5,
: when the repetition is allowed such that the number formed is divisible by
: 2 or 5 or both?
: A: 1500
個位一定要挑2,4,5,0
萬位一定要挑2,3,4,5
答案好像是4*5*5*5*4 = 2000而不是1500
: 4. In a school 5 colors are allotted to each house. If the flag of Tagore
: House has to be a sequence of three blocks of different colors, then how
: many colors can they choose from?
: A: 60
就直接5*4*3
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※ 編輯: ykshih 來自: 218.167.163.231 (03/01 12:27)
※ 編輯: ykshih 來自: 218.167.163.231 (03/01 12:29)
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