1057i knw a method...
first find all the prime factors of the required no nd den multiply the units digit of each of the factors....
but dats too tedius.....ne better method?
7@Ketan: I also know that method which u r talking about . find the prime factors divide by1019. . then taking the last digit of the remaining factors, multiplying them and getting the last digit of the product as the answer to the q.
3hmmm.
take modulo 10 after removing the powers of 10.
visit this link.
http://www.mathpages.com/home/kmath489.htm
here is a past year problem in AMC and its solution.
http://www.artofproblemsolving.com/Wiki/index.php/2010_AMC_10A_Problems/Problem_24