## Fundamentals of Physics Extended (10th Edition)

${2*\pi*radius}$ $={2*3.142*6370}$ $=40029\approx 40000$ km
Since we know that 1 kilometer = 1000 m, Earth's radius = 6370000 m= 6370 kilometers The formula for the circumference is 2*$\pi$*radius, Therefore, $2*\pi*radius={2*3.142*6370}=40029\approx 40000$ km