The Earth is approximately 8000 miles in diameter, so its circumference is approximately 8000·π = about 25,000 miles. Its surface area is approximately 4·π(4000 mi)<sup>2</sup> = 200,000,000 square miles. | The Earth is approximately 8000 miles in diameter, so its circumference is approximately 8000·π = about 25,000 miles. Its surface area is approximately 4·π(4000 mi)<sup>2</sup> = 200,000,000 square miles. |