Question

What is the digit at units place of 9^{81 ?}

Answer 1

Digit at ones place or you can also say unit digit.

In this question there are two cases.

1.) If n = even, then the unit digit is 1.

Example= 9^2= 81, 9^4= 6561, etc..

Here unit digit is 1.

2.) If n = odd, then the unit digit is 9.

Example= 9^1= 9, 9^3= 729, etc…

Here unit digit is 9.