Which of the following is a correct value for the Earth's circumference in kilometers?

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Multiple Choice

Which of the following is a correct value for the Earth's circumference in kilometers?

Explanation:
Think of a planet’s circumference as the distance around a circle with radius close to the planet’s radius. Use C = 2πR. Earth’s average radius is about 6,371 km, so C ≈ 2π × 6,371 ≈ 40,030 km. Rounded, that’s about 4.0 × 10^4 km, i.e., 40,000 km. This matches the commonly cited figure for Earth’s circumference. The other numbers are too large or too small by orders of magnitude: 4.0 × 10^3 km is about 4,000 km, far too small for a planet; 4.0 × 10^5 km is about 400,000 km, and 4.0 × 10^6 km is about 4,000,000 km—both far larger than Earth's actual circumference.

Think of a planet’s circumference as the distance around a circle with radius close to the planet’s radius. Use C = 2πR. Earth’s average radius is about 6,371 km, so C ≈ 2π × 6,371 ≈ 40,030 km. Rounded, that’s about 4.0 × 10^4 km, i.e., 40,000 km. This matches the commonly cited figure for Earth’s circumference.

The other numbers are too large or too small by orders of magnitude: 4.0 × 10^3 km is about 4,000 km, far too small for a planet; 4.0 × 10^5 km is about 400,000 km, and 4.0 × 10^6 km is about 4,000,000 km—both far larger than Earth's actual circumference.

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