What is the tens digit of 6^20? Answers.
A) 1
B) 3
C) 5
D) 7
E) 9
The tens digit of 6 in integer power starting from 2 (6^1 has no tens digit) repeats in a pattern of 5: {3, 1, 9, 7, 5}:   The tens digit of 6^2=36 is 3.   The tens digit of 6^3=216 is 1.   The tens digit of 6^4=...96 is 9.   The tens digit of 6^5=...76 is 7.   The tens digit of 6^6=...56 is 5.   The tens digit of 6^7=...36 is 3 again.   etc...   20 has the form 5n, so the tens digit of 6^20 is 7.   The answer is 7.
<result>D</result>
What is the tens digit of 6^20?