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The diameter of the Earth is approximately...
  • A
    12 700 km.
  • B
    6 350 km.
  • C
    18 500 km.
  • D
    40 000 km.

Refer to figure.
The diameter of Earth depends on where you are measuring it from. The Earth is not a perfect sphere, and so it has a different diameter around the equator than it does from pole to pole.

We know that at the Equator, 1º Longitude = 1NM. Based on that, the circumference of the Earth may be calculated as follows:

  • Earth circumference at the Equator = 360º x 60 NM = 21 600 NM => 21 600 NM x 1.852 = 40 000 km

Circumference = π x diameter (π = 3.14)
40 000 km = π x diameter
diameter = 40 000 km ÷ π
diameter = 12 732 km


Alternatively, you can just remember that the Earth's circumference (the distance all the way around the equator) is approximately 40 000 km (21 600 NM) and its diameter (the distance from one side to the other through Earth's center) is roughly 12 700 km.

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