Question

Find the remainder when $3^{40}$ is divided by 7?

• A. 3
• B. 4
• C. 1
• D. 5

Answer 1

The correct option is B 4

$3^{40}=3^1\times 3^{39}=3\times (3^3{)}^{13}=3\times (27{)}^{13}$
Now, when $(27{)}^{13}$ is divided by 7 it gives (-1) as remainder.
So, the remainder is (7-3) = +4.