If x^21
If x = 3^21 and y = 6^55, what is the remainder when xy is divided by 10?
(A) 2 (B) 3 (C) 4 (D) 6 (E) 8
My Ques: the final result that i get is 18/10 so when i reduce it in the lowest form i get 9/5 which gives 4 as remainder whereas 18/10 gives 8 as remainder and is the correct answer. Why cant we reduce it?
X=3^21. Units digit is 3.
Y=6^55. Units digit of Y is 6
Units place of XY is 8 (3×6=18. 8 remains as units digit. 1 is carried forward to tens)
XY/10 = 8/10 which leaves remainder of 8.
In my opinion, you cannot further reduce it because you are asked to divide it with 10. So performing long division with 10 leaves remainder 8.