Question

What is the remainder when $5^{79}$ is divided by 7?

• A. 1
• B. 5
• C. 4

Answer 1

The correct option is B 5

Using Fermat's theorem
$\frac{5^{79}}{7}=\frac{5^{78}\times 5}{7}=\frac{5^{6\left[13\right]}\times 5}{7}=\frac{1\times 5}{7}=5$