What is the area of a circle with radius 5?

Area of a circle = πr², where r is the radius. With r = 5: A = π(5)² = 25π square units. Numerically: 25π ≈ 25 × 3.14159 ≈ 78.5 square units. Common ASVAB answer choices keep π symbolic to avoid arithmetic ambiguity. Related circle formulas: (1) Diameter = 2r (twice the radius); (2) Circumference = 2πr or πd (length around the circle); (3) Area = πr² (surface inside); (4) Arc length = (θ/360) × 2πr where θ is the central angle in degrees; (5) Sector area = (θ/360) × πr². Common error: confusing radius and diameter — read the problem carefully. The constant π ≈ 3.14 ≈ 22/7 (older approximation); for precise work, calculator π. Squaring the radius first, then multiplying by π, avoids confusion.