document.write( "Question 843643: An ATM PIN consists of four digit chosen from 0-9, and repetition of a digit is allowed. How many PINs contain at least one \"7\"? \n" ); document.write( "
Algebra.Com's Answer #508285 by richard1234(7193)\"\" \"About 
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10^4 - (#pins containing no 7's)\r
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\n" ); document.write( "\n" ); document.write( "= 10^4 - 9^4\r
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\n" ); document.write( "\n" ); document.write( "= 10000 - 6561\r
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\n" ); document.write( "\n" ); document.write( "= 3439
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