Evaluate $\log_381$.
I notice that the base of the logarithm is 3, and I wonder if I can rewrite 81 as a power of 3. I recall that 81 is the same as 3 to the fourth power, so I can rewrite the logarithm as $\log_3(3^4)$. Now I can use the property of logarithms that says $\log_b(b^x) = x$, and apply it to this case. I get $\log_3(3^4) = 4$, which is the final answer. 