What is the square root of 81?

To determine the square root of 81, one must identify the number that, when multiplied by itself, equals 81.

In this case, 9 multiplied by 9 gives 81. Therefore, the square root of 81 is 9. This can be verified through basic multiplication:

9 × 9 = 81.

Thus, recognizing that the square root is derived from finding such a number confirms that the answer is indeed 9.

The other options, while they represent single-digit numbers, do not multiply to yield 81 when doubled. For instance, 7 x 7 equals 49, 8 x 8 equals 64, and 10 x 10 equals 100, none of which come close to 81. Therefore, 9 is the only correct and logical choice for the square root of 81.