Re: [問題] Please help a "vegetable bird" like me
我是這樣想
問說有六個字母:A B B C C C 可以怎排列
看你要先看三組中的哪組
假設就照A B C的順序
A有六個空間讓他排 所以是6種
B B有剩下的五個空間讓他們排 所以是C5取2
C C C有三個空間讓他們排 其實也只能有一種排法了 要寫成C3取3或直接寫成1都可
三組相乘 所以共60種方法
你要從B或C開始排也可 答案會一樣
※ 引述《RainySunDay (Heart fly)》之銘言：
: 1.How many different 6-letter sequences are there that consist of 1 A, 2 B's,
: and 3 C's?
: A:60
: 2.Apharmaceutical company received $3million in royalties on the firs $20
: million in sales of the generic equivalent of one of its products and then
: $9million in royalties on the next $108 million in saes. By approximately
: what percent did the ratio of royalties to sales decrease from the first $20
: million in sales to the next $108 million in sales?
: A:45%
: ps. The first question is I have a gap in memory of permutation formula
: The second question is I am a little bit confused with its meaning.
: Is the following equation right? [3/20-9/108]/ 9/108=87.5%
: Thanks for your patience.
--
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09/12 15:32, , 1F
09/12 15:32, 1F
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