Question

The remainder when $7^{98}$ is divided by 5 is

• A. 4
• B. 0
• C. 2
• D. 3

Answer 1

Answer: (A)

$7^{98}=(50-1{)}^{49}={}^{49}{C}_0(50{)}^{49}-{}^{49}{C}_1(50{)}^{48}+\dots ..+{}^{49}{C}_{48}\times 50-{}^{49}{C}_{49}$
Remainder $=5-1=4$