document.write( "Question 1169664: Find the units digit of the sum,$$ 1! + 2! + 3! + \cdots + 2006!. $$(latex)
\n" ); document.write( "Find the units digit of the sum, 1! + 2! + 3! + ... + 2006!.(not latex)
\n" ); document.write( "I am stuck. I cannot find a pattern because of the high numbers that this problem goes to. I have spent a lot of time, but haven't got anything. Thank you. \n" ); document.write( "

Algebra.Com's Answer #794462 by ikleyn(52814) $\"\"$ $\"About$

You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( " From the first glance, the problem seems to be hard, but . . . actually . . . it is a joke problem.\r
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document.write( "As soon as the last digit of n! is zero, it does not influence more on  the last digit of the sum . . . \r\n" );
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document.write( "So, the last requested digit comes from\r\n" );
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document.write( "    1! + 2! + 3! + 4! + 5! = 1 + 2 + 6 + 24 + 120 \r\n" );
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document.write( "and is,  T H E R E F O R E,   3.\r\n" );
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document.write( "ANSWER.  The last digit of  1! + 2! + 3! + . . .  + 2006!   is   .\r\n" );
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