document.write( "Question 1143784: In how many ways can 7 boys be seated in a row so that 3 boys are always seated together. \n" ); document.write( "
Algebra.Com's Answer #764701 by ikleyn(52787)\"\" \"About 
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\n" ); document.write( "In how many ways can 7 boys be seated in a row so that 3 \"highlight%28particular%29\" boys are always seated together.
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\n" ); document.write( "\n" ); document.write( "            Please pay attention on how I edited your post to make sense.\r
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\n" ); document.write( "\n" ); document.write( "            It is how a  Math problem  SHOULD  BE.\r
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document.write( "You actually consider permutations of (7-3+1) = 5 objects \"at the upper level\" (thinking about these 3 particular boys as one object) \r\n" );
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document.write( "and, in addition to it, you consider all permutations of these 3 particular boys \"at the bottom level\".\r\n" );
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document.write( "These permutations are independent, so you have, in all\r\n" );
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document.write( "    5!*3! = (1*2*3*4*5)*(1*2*3) = 120*6 = 720 permutations.       ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "On Permutations,  see introductory lessons \r
\n" ); document.write( "\n" ); document.write( "    - Introduction to Permutations\r
\n" ); document.write( "\n" ); document.write( "    - PROOF of the formula on the number of Permutations\r
\n" ); document.write( "\n" ); document.write( "    - Problems on Permutations\r
\n" ); document.write( "\n" ); document.write( "    - Arranging elements of sets containing indistinguishable elements \r
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\n" ); document.write( "\n" ); document.write( "    - OVERVIEW of lessons on Permutations and Combinations\r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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\n" ); document.write( "\n" ); document.write( "Also,  you have this free of charge online textbook in ALGEBRA-II in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this online textbook under the topic  \"Combinatorics: Combinations and permutations\". \r
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\n" ); document.write( "\n" ); document.write( "Save the link to this textbook together with its description\r
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\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-II
\n" ); document.write( "https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson\r
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\n" ); document.write( "\n" ); document.write( "into your archive and use when it is needed.\r
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