make r the subject of this formula?

Question

i have a question

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Make r the subject

S=4(the pie symbol)r(^2)

Can you give clear instructions on how to do the method please.
No calculator allowed.
thanks

Answer 1

Start with:
S = 4 π r²

You want to isolate r by itself. Divide both sides by 4π it moves to the other side:
S / 4π = r²

Now take the square root of both sides so that you have r, instead of r²:
√(S / 4π) = r

Reverse the order:
r = √(S / 4π)

Note: S is the formula for the surface area of a sphere. Using this formula in terms of r, you can now figure out the radius of a sphere given its surface area.

Answer 2

First divide both sides by 4 π and then square root both sides

S/ (4π) = r^2
√(s / 4π) = r

Answer 3

S=4pi*(r^2)
r^2 = S/(4pi)
r = sqrt{S/(4pi)}