3^201 mod 11 = A. 3 B. 5 C. 6 D. 10 I got this question during

3-201-mod-11-a-3-b-5-c-6-d-10-i-got-this-question-during

3^201 mod 11 =

A. 3

B. 5

C. 6

D. 10

I got this question during an online exam.

Question is from Number Theory in portion More Number Theory of Cryptograph & Network Security

The correct choice is A. 3

The explanation is: Use Fermats Theorum. Fermat’s Theorem states that if p is prime and a is a positive integer not divisible

by p, then a^(p–1) = 1 (mod p). Therefore 3^10 = 1 (mod 11). Therefore

3^201 = (3^10)^20 x 3 = 3 (mod 11).