A square is inscribed in a circle. If the area of the square is 36 square units, what is the area of the circle?

✓ Correct Answer: Option C

If the square's area is 36, its side is 6. The diagonal of the square, 6√2, is the diameter of the circle. The radius is (6√2)/2 = 3√2. The area of the circle is πr² = π(3√2)² = 18π.