The unit digit of $122^{159}$ is:

Question

The unit digit of $122^{159}$ is:

Option A

2

Option B

4

Option C

6

Option D — Correct answer

8

Correct choice.

Explanation

For powers ending in $2$, the unit-digit cycle is $2,4,8,6$ with period $4$. Since $159\mod4=3$, use the third term of the cycle, which is $8$.

Chapter Mock 1: Number System, Simplification and Approximation