Question

Find the unit digit of $8^{25}$

• A. $4$
• B. $8$
• C. $6$
• D. $2$

Answer 1

The correct option is B $8$

Possibilities of unit digit of $8^n$ are $8,4,2$ and $6$. The unit digit of $8^n$ gets repeated after every $4^{th}$ power of $8$.
$\therefore$ Remainder obtained when $25$ is divided by $4$ is $1$.
$\therefore 8^{25}=8^{4\times 6+1}=8^1$
$\therefore$ The unit digit of $8^{25}$ is $8$.