document.write( "Question 1029343: How many 3-digit numbers are multiple of 21?
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Algebra.Com's Answer #644374 by Edwin McCravy(20056)\"\" \"About 
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document.write( "The smallest 3-digit number is 100 and the largest\r\n" );
document.write( "3-digit number is 999.\r\n" );
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document.write( "Dividing 100 by 21 gives 4.76, which rounds up to 5,\r\n" );
document.write( "so the smallest 3-digit multiple of 21 will be 5*21 or 105.\r\n" );
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document.write( "Dividing 999 by 21 gives 47.57, which rounds down to\r\n" );
document.write( "47, so the largest 3-digit multiple of 21 will be 47*21 or 987.\r\n" );
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document.write( "So the 3-digit multiples of 21 form the arithmetic sequence \r\n" );
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document.write( "5*21,6*21,...,46*21,47*21\r\n" );
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document.write( "Dividing them all by 21 gives the sequence\r\n" );
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document.write( "5,6,...,46,47, which has the same number of terms.\r\n" );
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document.write( "Subtracting 4 from each gives the sequence\r\n" );
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document.write( "1,2...,42,43, which also has the same number of terms.\r\n" );
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document.write( "Answer: 43\r\n" );
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document.write( "Edwin
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