document.write( "Question 960346: You download 15 music files on your computer and plan to save 7 of them to an mp3 player. In how many ways can u arrange the songs. I need to know how many ways anfd if it is a Combination or a Permutation
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Algebra.Com's Answer #586892 by Edwin McCravy(20055)\"\" \"About 
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You download 15 music files on your computer and plan to save 7 of them to an
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document.write( "Whether it is a combination or permutation depends on YOU, as to whether\r\n" );
document.write( "YOU care what order they are downloaded in or not.\r\n" );
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document.write( "If YOU care what order they are dowloaded in, then it is a permutation.\r\n" );
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document.write( "15 Position 7 = 15P7 = .\r\n" );
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document.write( "That's 3991680 PERMUTATIONS of 15 things taken 7 at a time. \r\n" );
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document.write( "If YOU DON'T care what order they are in, then it is a combination.\r\n" );
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document.write( "15 Choose 7 = 15C3 =  \r\n" );
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document.write( "You can cancel all those factors in the bottom into the factors in the top\r\n" );
document.write( "and you'll always end up with a whole number.\r\n" );
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document.write( "That's only 792 PERMUTATIONS of 15 things taken 7 at a time.  It's much\r\n" );
document.write( "less because you don't care what order they are downloaded in.\r\n" );
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document.write( "Notice that the numerator of the combination formula is the same as the\r\n" );
document.write( "permutation formula.  The denominator of the combination formula takes\r\n" );
document.write( "away all the different orderings of each set of songs.\r\n" );
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document.write( "Edwin
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