<p>If n is a positive integer, which of the following CANNOT be the units digit of 3^n?</p>
<p>A) 1
B) 3
C) 5
D) 7
E) 9</p>
<p>--- Tbh I don't understand this question :(</p>
<p>This question asks you to determine a pattern. You should test few positive numbers and see what pattern appears when you raise 3 by these numbers. </p>
<p>3^1 = 3
3^2 = 9
3^3 = 27
3^4 = 81
look to the unit digits and see that the pattern starts to repeat itself
3^5 = 243
3^6 = 729
3^7 = 2187
3^8 = 6561</p>
<p>you see, the pattern is 3, 9, 7, 1 and then it repeats like this forever. So 5 cannot be and C is the correct answer.</p>
<p>3^n is not a multiple of 5, so the answer is C.</p>
<p>The other units digits (1,3,7,9) can be obtained using Aimingat750’s method.</p>
<p>Thank you guys :)</p>