Back to Rearrange formulas — Problem 2 · Task Set 29

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Grade 9·8 problems·~12 min·Common Core Math - HS Algebra·standard·hsa-ced-a-4

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Procedures

The area of a circle is $A = \pi r^2$ . To rearrange this formula to
solve for $r$ , which sequence of steps is correct?

Subtract $\pi$ from both sides: $A - \pi = r^2$ ; then take the
square root: $r = \sqrt{A - \pi}$ .

Divide both sides by $\pi$ : $\frac{A}{\pi} = r^2$ ; then take the
square root: $r = \sqrt{\frac{A}{\pi}}$ .

Divide both sides by $\pi$ : $\frac{A}{\pi} = r^2$ ; then the answer
is $r = \frac{A}{\pi}$ (no square root needed).

Take the square root of both sides first: $\sqrt{A} = \sqrt{\pi} r$ ;
then divide by $\sqrt{\pi}$ : $r = \frac{\sqrt{A}}{\sqrt{\pi}}$ .