Question

The unit digit in $7^{1018}$ is

• A. $7$
• B. $9$
• C. $3$
• D. $1$

Answer 1

The correct option is B $9$

The unit digit iini $7^1=77^2=97^3=37^4=17^5=7$

So the series is circular $7,9,3,1,7,9,3,1,7,9,3,1,\mathrm{7...}$

So the unit digit in $7^{1018}$ is given by remainder of $\frac{1018}{4}$ is $2$

$7^2=49$ so the unit digit is $9$