To evaluate the logarithm $\log_3 81$, we are finding the power to which the base 3 must be raised to result in 81. This can be expressed as:

$\log_3 81 = x \implies 3^x = 81$

We now solve for $x$:

1. Rewrite 81 as a power of 3: $81 = 3^4$

2. Substitute into the equation: $3^x = 3^4$

3. Since the bases are the same, the exponents must be equal: $x = 4$

Thus, $\log_3 81 = 4$.

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Do you want further details or additional examples? Here are related questions for practice:

1. Evaluate $\log_2 32$.
2. Solve $\log_5 125$.
3. Simplify $\log_{10} 1000$.
4. Determine $\log_4 16$.
5. Compute $\log_2 8 + \log_2 4$.

Tip: To quickly solve logarithms, try expressing the number as a power of the base!