2024/006) Show that $10^{th}$ digit of a power of 3 is always even

The power of digit of 3 shall have 1 or 3 or 7 or 9 as the unit digit.

Let us see some power of 3 that is 1,3,27,81(after this the sequence in the 1st digit repeats.

So we have (20n + x) where x is 1 or 3 or 7 or 9.

When we multiply by 3 we get 60n + 3 or 60n + 9 or 60n + 21 or 60n + 27 that is 60n + 3 or 60n + 9 or 20(3n+1) + 7 or 20(3n+1) + 9

So tens digit is even