SOLUTION: Find the volume of a sphere with a diameter of 20 km.

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Question 117074: Find the volume of a sphere with a diameter of 20 km.
Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
Wow! That's a pretty big sphere. A diameter of 20 km is equivalent to a diameter of almost 12.5 miles!
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Anyhow, the formula for the volume (V) of a sphere is:
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V+=+%284%2F3%29%2Api%2Ar%5E3
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where V is the volume and r is the radius of the sphere.
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If the diameter of a sphere is 20 km, then the radius of that sphere is half that or the radius
of the given sphere is 10 km.
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Substituting 10 km for r in the volume equation results in:
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V+=+%284%2F3%29%2Api%2A10%5E3
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and 10%5E3+=+10+%2A+10%2A10+=+1000
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This says that we can substitute 1000 for r%5E3 in the formula to get:
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V+=+%284%2F3%29%2Api%2A1000
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Multiplying the 1000 times the %284%2F3%29 results in %284000%2F3%29 and dividing the
4000 by 3 results in 1333.33333333. Substituting 1333.33333333 for %284%2F3%29%2A1000
reduces the equation to:
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V+=+%281333.33333333%29%2Api
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and using a scientific calculator we can multiply out 1333.33333333 times pi to get:
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V+=+4188.790205
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And since the radius was in kilometers this answer is in cubic kilometers. So the answer to
this problem is:
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Volume = 4188.790205 cubic kilometers
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Hope this helps you to understand the problem a little better.
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