Question 621978
*[tex \LARGE 3^0 \equiv 1 (mod 10)]
*[tex \LARGE 3^1 \equiv 3]
*[tex \LARGE 3^2 \equiv 9]
*[tex \LARGE 3^3 \equiv 7]
*[tex \LARGE 3^4 \equiv 1], the process repeats every 4.


*[tex \LARGE 855 \equiv 3 (mod 4)] so *[tex \LARGE 3^{855}] will have the same units digit as *[tex \LARGE 3^3], or 7.