If the diameter of a circular pond is 10 feet, what is its area?

To find the area of a circular pond, the relevant formula is A = πr², where A represents the area and r is the radius of the circle.

Since the diameter of the pond is given as 10 feet, the radius is half of the diameter. Thus, the radius is calculated as follows:

Radius (r) = Diameter / 2 = 10 feet / 2 = 5 feet.

Now, you can substitute the radius into the area formula:

A = π(5 feet)² = π(25 square feet).

Using the approximate value of π (approximately 3.14):

A ≈ 3.14 × 25 = 78.5 square feet.

Therefore, the area of the circular pond is 78.5 square feet. This shows that the correct choice is indeed the one that reflects this calculation, leading to the conclusion that the area is C, 78.5 feet squared.