(In reply to

Puzzle Solution by K Sengupta)

At the outset, we have:

11^2003 times 7^2004 times 13^2005

= (11*7*13)^2003 times 7 times 13^2

= (1001)^2003 times (7*13) times 13

= (1001)^2003 times 91 times 13

Now,we observe that:

The last digit of 1001^2003 is 1

The last digit of 91 is 1

The last digit of 13 is 3

Consequently, the required last digit of the given expression

= 1*1*3

= 3