document.write( "Question 658540: the number of ways in which four letters of the word 'MATHEMATICS'can be arranged .answer is 2454 pls solve this\r
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Algebra.Com's Answer #410324 by MathLover1(20849)\"\" \"About 
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I assume, for ordered combinations (i.e. permutations).\r
\n" ); document.write( "\n" ); document.write( "Removing the duplicate \"M\",\"+A\" and \"T\", we have \"8\" different letters from which we can make \r
\n" ); document.write( "\n" ); document.write( "[8]P[4]=\"+8%21%2F4%21=+1680\" permutations.\r
\n" ); document.write( "\n" ); document.write( "We need to \"add\" words having two \"M\"'s and two other distinct letters:\r
\n" ); document.write( "\n" ); document.write( "Pick two spots for the \"M\"'s ([4]C[2] ways) and then assign the \"7\" other letters the two other spots ([7]P[2]). \r
\n" ); document.write( "\n" ); document.write( "So, we have ([4]C[2])([7]P[2]) = \"6+%2A+42+=+252\" more possibilities.\r
\n" ); document.write( "\n" ); document.write( "We do the same for words with two \"A\"'s and those with two \"T\"'s, so we're now at \"1680+%2B+3%2A252+=+2436\".\r
\n" ); document.write( "\n" ); document.write( "We also need to \"add\" words having pairs of \"identical\"\"+letters\" like MAMA and TAAT... \r
\n" ); document.write( "\n" ); document.write( "For two \"M\"'s and two \"A\"'s, there are [4]C[2]=\"6\" possibilities. Same for \"M\"'s and \"T\"'s, and same for \"A\"'s and \"T\"'s.
\n" ); document.write( "This add \"18\" to our total.\r
\n" ); document.write( "\n" ); document.write( "so, we have
\n" ); document.write( "\"2436%2B18=2454\"\r
\n" ); document.write( "\n" ); document.write( "Answer: \"2454\"\r
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