document.write( "Question 823952: there are k different books and i copies of each in a library. the number of ways in which a student can make selection of one or more book is \n" ); document.write( "
Algebra.Com's Answer #495954 by Edwin McCravy(20060)\"\" \"About 
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there are k different book titles and i copies of each title.
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document.write( "for each of the k titles we can answer this pair of questions:\r\n" );
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document.write( "A. Will I select a book with this title?\r\n" );
document.write( "B. Will I NOT select a book of this title?\r\n" );
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document.write( "in two ways, either YES or NO.\r\n" );
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document.write( "The number of ways in which a student can make a selection of one or\r\n" );
document.write( "more books is 2×2×2×···×2 where there are k 2's all multiplied together.\r\n" );
document.write( "So there are 2k ways to select k titles. Suppose the copies of each\r\n" );
document.write( "title are numbered 1 through i.  The for each of those 2k ways to\r\n" );
document.write( "select a title, there are i ways to select a copy number.  So the answer is \r\n" );
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the number of ways in which a student can make selection of one or more books is
2k*i - 1
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document.write( "Why the -1?  Because we must subtract the number of ways he answers \"no\" to\r\n" );
document.write( "question B all k times, which is 1 way.  If he answers \"no\" to them all, he\r\n" );
document.write( "walks out of the library empty-handed. If you want to count that case as\r\n" );
document.write( "an \"empty selection\", then it's: \r\n" );
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document.write( "2k*i\r\n" );
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document.write( "without the -1.    \r\n" );
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document.write( "Edwin
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