If a circle has radius 5 cm, what is its area? Use π ≈ 3.14.

If a circle has radius 5 cm, what is its area? Use π ≈ 3.14.

• A. 70.0
• B. 78.0
• C. 78.5
• D. 80.0

Answer: (C)

Area of a circle comes from A = π r^2. With a radius of 5 cm, you substitute: A ≈ 3.14 × (5)^2 = 3.14 × 25 = 78.5 square centimeters. So using π ≈ 3.14 gives 78.5 cm^2, which is why that value is the correct area. The area grows with the square of the radius, so changing the radius has a big effect.

Area of a circle comes from A = π r^2. With a radius of 5 cm, you substitute: A ≈ 3.14 × (5)^2 = 3.14 × 25 = 78.5 square centimeters. So using π ≈ 3.14 gives 78.5 cm^2, which is why that value is the correct area. The area grows with the square of the radius, so changing the radius has a big effect.