What is the square root of 81?

• A. 7
• B. 8
• C. 9
• D. 10

Answer: (C)

The square root of a number is a value that, when multiplied by itself, returns the original number. In the case of 81, the square root is 9 because when you multiply 9 by 9, you obtain 81 (9 × 9 = 81). This characteristic defines how square roots work; they identify the number that, when squared, yields the target number.

Understanding that 9 multiplied by itself gives 81 can help you quickly recognize that 9 is the correct answer. The other values, such as 7, 8, and 10, do not yield 81 when squared. For example, 7 × 7 equals 49, 8 × 8 equals 64, and 10 × 10 equals 100. Thus, these options do not meet the criteria of being the square root of 81.