A square has an area of eighty-one square feet. What is the perimeter of the square?

To find the perimeter of a square when you know its area, it’s essential to start with the relationship between the area and the side length of the square. The area ( A ) of a square is given by the formula ( A = s^2 ), where ( s ) is the length of one side of the square.

In this case, the area is given as eighty-one square feet. To find the side length, you take the square root of the area:

[

s = \sqrt{81} = 9 \text{ feet}

]

Next, to calculate the perimeter ( P ) of the square, you use the formula:

[

P = 4s

]

Substituting the side length we found:

[

P = 4 \times 9 = 36 \text{ feet}

]

Therefore, the perimeter of the square is 36 feet. This makes the choice the correct answer.

The other options do not result from the calculations based on the area provided and therefore do not represent the perimeter of a square with that area.