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Earth, circumference

What is the circumference of the Earth? How far around is the Earth?

The average radius of the Earth is 3,959 miles (6,374 kilometers).
The equitorial diameter of the Earth (distance from one side of the Earth to the other at the equator) is about 7,926 miles.

The ratio of the circumference to the diameter of a circle (circumference/diameter)
is written as the symbol pi.
Pi is approximately 3.141592.

Therefore, to determine the circumference from the diameter given above:
equitorial diameter x 3.141592 = equitorial circumference
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7,926 x 3.141592 = 24,900
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The earth has a circumference of approximately 24,900 miles.

More precisely the circumference of the earth
at the equator is 24,902 mi
/ 40,076 km.


How fast would you have to travel to see the sun set twice,
or outrun the shadow of the setting sun?

Since the sun "travels" once around the earth every 24 hours,
we can get the speed by dividing the circumference of the earth by 24:

miles divided by hours
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24,900 / 24 = 1,038 miles per hour

A RATIO of a to b can be expressed in three ways:
1. a : b
2. a / b
3. a ÷ b

The distance from Los Angeles, California to New York City, N.Y., is 2462 miles (3961 km).


128,000 Digits of Pi
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Yahooligans Reference Shelf