document.write( "Question 643218: how many 3 digit numbers can be formed using 0-9 with at least 1 repeating digits? \n" ); document.write( "
Algebra.Com's Answer #404626 by AnlytcPhil(1806)\"\" \"About 
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how many 3 digit numbers can be formed using 0-9 with at least 1 repeating digits?
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document.write( "1. First, we find the number of 3 digit numbers.\r\n" );
document.write( "2. Second, we find the number of 3 digit numbers with NO repeating digits.\r\n" );
document.write( "3. Third, we subtract the result of 2 from the result of 1 \r\n" );
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document.write( "1. There are two ways to do step 1\r\n" );
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document.write( "   A. there are 999 1 digit, 2-digit and 3-digit numbers.\r\n" );
document.write( "      there are 99 of these which are not 3 digits\r\n" );
document.write( "      we subtract 99 from 999 and get 900\r\n" );
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document.write( "   B. There are 9 ways to pick the first digit, 10 ways to pick the\r\n" );
document.write( "      second digit, and 10 ways to pick the thrid digit, so that's\r\n" );
document.write( "      91010 = 900.\r\n" );
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document.write( "      Either way you get 900 3-digit numbers\r\n" );
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document.write( "2. To do step 2, there are 9 ways to choose the first digit,\r\n" );
document.write( "   (can't choose 0), 9 ways to choose the 2nd digit (can choose 0),\r\n" );
document.write( "   and 8 ways to choose the third digit.  That's 998 = 648\r\n" );
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document.write( "3.  900 - 648 = 252   \r\n" );
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document.write( "Edwin
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