To find your answer, you want to get everything but the variable "d," the diameter, onto one side of the equal sign, leaving d by itself.
1) Start by multiplying both sides by 4 to get rid of the 4 in the denominator on the right. bringing it to the other side:
[tex]A = \frac{1}{4} \pi d^{2} \\
4(A) = 4(\frac{1}{4} \pi d^{2} )\\
4A = \pi d^{2} [/tex]
2) Divide both sides by π to move the π to the other side of the equation (I put the d squared on the left, but you can keep it on the right):
[tex]4A = \pi d^{2} \\
d^{2} = \frac{4A}{ \pi } [/tex]
3) Finally, take the square root of both sides to get the value of d:
[tex]d^{2} = \frac{4A}{ \pi } \\
d = \sqrt{\frac{4A}{ \pi } } [/tex]
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Answer: [tex]d = \sqrt{\frac{4A}{ \pi } } [/tex]
