The Units Digit

n! = 1.2.3.......(n-1).n
So 1! =1 2! = 2 3! = 6 4! = 24 5! = 120
We know (2^x).(5^y) always ends with zero...
So from 5! the units digit will have at least one '0'...
So adding ! + 2! + 3! + 4! = 1+2+6+24 = 33
Adding all we get a number which will have in its units place 3

The unit digit of 1! Is 1, 2! Is 2, 3! Is 6, 4! Is 4, 5! Is 0 and the followings have 0 as their unit digits. Therefore the final answer is the unit digit of 1 + 2 + 6 + 4, which is 3