1. The problem is to find the value of $\sqrt{81}$.\n\n2. The square root of a number $x$ is a value that, when multiplied by itself, gives $x$.\n\n3. We use the formula $\sqrt{a} = b$ where $b^2 = a$.\n\n4. Here, $a = 81$. We need to find $b$ such that $b^2 = 81$.\n\n5. Since $9 \times 9 = 81$, we have $\sqrt{81} = 9$.\n\n6. Therefore, the final answer is $9$.