Yahoo Answers: Answers and Comments for Permutation/Combination [數學]
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https://answers.yahoo.com/question/index?qid=20100315000051KK01881
From chi kio
enUS
Mon, 15 Mar 2010 23:46:20 +0000
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Yahoo Answers: Answers and Comments for Permutation/Combination [數學]
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https://answers.yahoo.com/question/index?qid=20100315000051KK01881
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From chi kio: thq so much!!!!! i fully understand now! =D
https://answers.yahoo.com/question/index?qid=20100315000051KK01881
https://answers.yahoo.com/question/index?qid=20100315000051KK01881
Tue, 16 Mar 2010 01:08:18 +0000
thq so much!!!!! i fully understand now! =D

From ☂雨後晴空☀: 1)Find all the numbers from 1 to 999 in which ...
https://answers.yahoo.com/question/index?qid=20100315000051KK01881
https://answers.yahoo.com/question/index?qid=20100315000051KK01881
Tue, 16 Mar 2010 00:12:34 +0000
1)Find all the numbers from 1 to 999 in which all the digits are different.
For 3 digits numbers : The leading digit can be 1 to 9 (9 cases)
The 2nd digit can be 0 to 9 but no repeat the leading digit (9 cases)
The last digit can be 0 to 9 but no repeat other digits (8 cases)
9 * 9 * 8 = 648 numbers
For 2 digits numbers : 9*9 = 81 numbers
For 1 digit numbers : 1  9 total 9 numbers
There are 648 + 81 + 9 = 738 numbers
2)The leading 3 letters have 26^3 cases
An integer have 999 cases
The last letter have 26 cases
Total (26^3) (999) (26) = 999 x 26^4 different registration numbers that could be formed.
3)Find also in how many ways of these registration numbers the letters and digits are all different.
The leading 3 letters have 26 x 25 x 24 cases
An integer have 738 cases (By question 1 result.)
The last letter have 23 cases ( no repeat with first 3 letters)
Total (26 x 25 x 24) x (738) x (23) = 23x24x25x26x738 registration numbers the letters and digits are all different.