(3) 25,000 km Explanation: The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers). But, if we measure the earth through the poles the circumference is a bit shorter - 24,859.82 miles (40,008 km). Thus, the earth is a tad wider than it is tall, giving it a slight bulge at the equator. This shape is known as an ellipsoid or more properly, geoid (earth-like).