What is the area of the circle with a diameter of 20 feet?

• A. 628 sq ft
• B. 157 sq ft
• C. 314 sq ft
• D. 200 sq ft

Answer: (C)

Area of a circle is π times the radius squared. Since the diameter is 20 ft, the radius is 10 ft. So the area is π × 10^2 = 100π square feet, which is about 314 square feet. The other numbers come from common mistakes, like using the diameter in place of the radius or squaring the wrong dimension, which is why they don’t match the correct calculation.