54 lines
1.5 KiB
Plaintext
54 lines
1.5 KiB
Plaintext
<pre>
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ABCD
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CABD
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ACDB
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DACB
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BCDA
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ACBD
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ADCB
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CDAB
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DABC
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BCAD
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CADB
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CDBA
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CBAD
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ABDC
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ADBC
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BDCA
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DCBA
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BACD
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BADC
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BDAC
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CBDA
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DBCA
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DCAB
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</pre>
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Listed above are all-but-one of the permutations of the symbols '''A''', '''B''', '''C''', and '''D''', ''except'' for one permutation that's ''not'' listed.
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;Task:
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Find that missing permutation.
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;Methods:
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* Obvious method:
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enumerate all permutations of '''A''', '''B''', '''C''', and '''D''',
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and then look for the missing permutation.
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* alternate method:
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Hint: if all permutations were shown above, how many
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times would '''A''' appear in each position?
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What is the ''parity'' of this number?
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* another alternate method:
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Hint: if you add up the letter values of each column,
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does a missing letter '''A''', '''B''', '''C''', and '''D''' from each
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column cause the total value for each column to be unique?
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;Related task:
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* [[Permutations]])
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<br><br>
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