Surface area

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notsosmrt

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Can someone explain how to find the surface area of a hemishpere with an area of 121 mm(2)
 
If you are given that the surface area is 121 square millimeters, then why are you trying to find the surface area?

Eliz.
 
Hello, notsosmrt!

Can someone explain how to find the surface area of a hemisphere with an area of 121 mm<sup>2</sup>?
Click to expand...
I may be missing something, but isn't the area \(\displaystyle 121\,mm^2\)?
 
I love Geometry! ^_^ Was my favorite subject in the math course. :p I totally aced it.

Now, what you need to do, is reverse the problem. You're gonna take the area, and set it equal to the equation of a sphere

You have to take the area, and set it equal to the equation area = pi * r^3.

M'kay

So, we have 121 = 3.14159265358979323846264338379502884 (R^3)

Subtract pi. (I'll use 3.14 for you. ;))

We get 117.86. M'kay.

Now, we need to find the cubed root of 117.86, and we will get the radius of the sphere.

We get something like 4.902, or something. (I'm doing this in my head -- sorry if it's wrong)

Now we use the equation to find surface area of a sphere. :)

SA = 4/3 * Pi * R^3

SA = 493.411 / 2 (Since it's a hemisphere)

The answer is 246.7 mm^2 :)

I hope this has helped you, and it has certainly satisfied me. :D
 
That's lovely, but you appear to have made up your own question.

Soroban and Stapel have given most adequate direct responses. Read them carefully until you figure out that the problem statement is a bit odd.
 
Gir489: How did you ace it without mastering the difference between pi + and pi * ?
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Gene
 
Gir489:
Quote:
area = pi * r^3.
So, we have 121 = 3.14159265358979323846264338379502884 (R^3)
Subtract pi...

How about divide by pi instead? :evil:
 
gir489 said:
He said the Hemisphere's AREA was 121 MM.[sic]
He's asking for the SURFACE AREA.
Click to expand...
Yes. He gave the area, and then asked for the area. As mentioned previously, this does not make much sense.

Eliz.
 
I suppose I could guess about this too, but the only one who knows is strangely silent. Toosmrt to join in?
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Gene
 
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