the last digit in S=sum(n=1 to 99) n! = the last digit in S=sum(n=1 to 4) n!, because the last digit of (n=5 to 99) n! are all 0.
Therefore the answer is 3
blackjack
<a href="http://c.casalemedia.com/c?s=51816&f=3&id=0" target="_blank"><img src="http://as.casalemedia.com/s?s=51816&u=http://perplexus.info&f=3&id=0&if=0" width="120" height="600" border="0"></a>
flooble's webmaster puzzle
Answer
