Question

The last digit in $7^{300}$ is

• A. 7
• B. 9
• C. 1
• D. 3

Answer 1

Answer: (C)

We have, $7^1=7,7^2=7\times 7=49$
$7^3=7\times 7\times 7=343;$
$7^4=7\times 7\times 7\times 7=2401$
$7^5=7\times 7\times 7\times 7\times 7=16807$
Last digit of $7^1=7,7^2=9,7^3=3,7^4=1$ and $7^5=7$ thus cycle of last digit repeats at $7^5.$
$\therefore$ Last digit of $7^{300}=1$