Question

find the unit digit of 8 to the power 243

Answer 1

Hey Devansh,

Let's learn cyclicity of 8 first,

Unit digit of

8^(4k)=_6,

8^(4k+1)=_8,

8^(4k+2)=_4

8^(4k+3)=_2.

Now,8^243 On dividing the power 243by 4, remainder we get is 3.

So, it can be written in the form of

8^(4k+3) .And we know that unit digit of 8^(4k+3) =_2.

So, unit digit of 8^(243) is 2.

Hope it helps