Instructables

Surface Area of a Sphere

Step 3: Reversing the Action

Picture of Reversing the Action
Now say we have the surface area-("1000") and we need to find the radius. This is what we got to do.

Before we move on, check out the formula down below...Study it...Lodge it into your brain...Make sure you can recite it back to me...in your sleep...hopping on one foot...while burping...and wearing an eye patch because you went cow tipping and the cow fought back. If you can do that you're ready to move on...If not, I'll wait.
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>>>>> In words, the formula is radius is equal to the square root of the dividend of the surface >>>>> area and the quotient of 4 and pi
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Took you long enough. Ok back to business.
We know the surface area, "1000", and we know pi*4=12.56

So we have to take the 1000 and divide it by 4(pi):

1000/12.56=79.61

So now we take our new answer (79.61) and find the square root for that:

=8.92

And there we go...Our radius is "8.92"
Wahoo...Now go around and show everyone your knowledge. Hehe

Optional: To find out how and why we have our original formula...Go to the next step
 
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