by klebian » Tue Mar 23, 2010 10:56 am
Let's see if we can find a pattern. 9 = 9 (mod 1000), 9*99 = 891 (mod 1000), 9*99*999 = 109 (mod 1000), 9*99*999*9999 = 891 (mod 1000). So it alternates between 109 and 891, and the answer is [unparseable or potentially dangerous latex formula].