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Permutations

by ruthm_24 » Sat Oct 02, 2010 10:24 am
All of the stocks on the over-the-counter market are designated by either a 4-letter or a 5-letter code that is created by using the 26 letters of the alphabet. Which of the following gives the maximum number of different stocks that can be designated with these codes?
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by Arcane66 » Sat Oct 02, 2010 10:58 am
Hmm, is the answer 8,252,400? I got this by using the permutation formula twice. 26!/(26-4)! + 26!/(26-5)!. I
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by ruthm_24 » Sat Oct 02, 2010 11:09 am
Sorry, forgot to post that the answer is [spoiler]27(26^4)[/spoiler].
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by sanabk » Mon Oct 04, 2010 3:49 pm
4-letter code
=26 x 26 x 26 x 26
=(26)^4

5-letter code
=26 x 26 x 26 x 26 x 26
=(26)^5

Total=(26)^4 + (26)^5
= (26)^4 + 26 x (26)^4
=(26)^4 [1+26]
=27 x (26)^4
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by lokesh r » Tue Oct 05, 2010 7:15 am
sanabk wrote:4-letter code
=26 x 26 x 26 x 26
=(26)^4

5-letter code
=26 x 26 x 26 x 26 x 26
=(26)^5

Total=(26)^4 + (26)^5
= (26)^4 + 26 x (26)^4
=(26)^4 [1+26]
=27 x (26)^4
Hey i think u are assuming repitition allowed, but question does not explicitly mention that repitition is allowed.
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by Tani » Tue Oct 05, 2010 10:58 am
UNless the questions tells you that you cannot repeat a letter, then repetition is possible. You can't assume an unstated restriction.
Tani Wolff
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