What is the units digit of (3^13)(4^13)? Options
A) 2  B) 4  C) 6  D) 7  E) 8
-&gt; The ones place of (~3)^n repeats after 4 times like 39713.   The ones place of (~4)^n repeats after 2 times like 464.   Then, 3^13=3^4*3+13^1.,   4^13=4^2*6+1=4^1=~4   which is (3^13)(4^13) (3^1)(~4)=(~3)(~4)=~2. Therefore, the answer is 2.
<result>A</result>
What is the units digit of (3^13)(4^13)?