document.write( "Question 1088525: How many 4 digit number are there when a digit may be repeated any number of times \n" ); document.write( "
Algebra.Com's Answer #702798 by math_helper(2461)\"\" \"About 
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If we assume the leading digit can not be zero, then the first 4-digit number is 1000.
\n" ); document.write( "The last 4-digit number is 9999.
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\n" ); document.write( "The number of 4-digit numbers is therefore:
\n" ); document.write( "9999 - 1000 + 1 = \"+highlight%289000%29+\"\r
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\n" ); document.write( "Another way to calculate this:
\n" ); document.write( " 1..9 are available for the first digit —> 9 choices
\n" ); document.write( " 0..9 are available for the 2nd, 3rd, and 4th digits —> 10 choices for each: 10*10*10 = 1000 choices total
\n" ); document.write( "and 9*1000 = 9000.
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