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Answer
90^468 can be written as (9X10)468
Now the number will have 468 zeroes in the left because of 10^468.
So basically the question is to find the unit digit of 9^468 or 3^936.
powers of 3 has cyclicity.
3,9,7,1,3,9,7,1,3,9,7,1....
After every 4 terms, the series repeat.
936 is divisible by 4. This means that the last term will correspond to 4th term in the cycle, i.e. 1
So the answer is 1.
