What is the sum of the final three digits of the integer representation of 5^100?
Note the pattern
5^1 = 5
5^2 = 25
5^3 = 125
5^4 = 625
5^5 = 3125
5^6 = 15625
5^7 = 78125
5^8 = 390625
So...it appears that for n ≥ 2, 5^(2n) will end in ....625
So....5^(2 * 50) = 5^100 ends in 625
And the sum is 6 + 2 + 5 = 13
+586 
