Which expression represents the area of a circle?

• A. P = 4s
• B. P = 2l + 2w
• C. A = π r^2
• D. P = a + b + c

Answer: (C)

The space inside a circle, its area, is given by multiplying pi by the radius squared. The radius is how far it reaches from the center to the edge, and pi is that constant that links a circle’s measurements; squaring the radius shows how area grows with size. So the direct expression for the circle’s area is A = π r^2.

The other expressions describe different ideas: one is the perimeter of a square, another is the perimeter of a rectangle, and the last sums three sides, which would relate to a triangle’s perimeter, not the circle’s area. If you know the diameter instead of the radius, you can still use the same idea with A = π (d/2)^2.