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Mathematics 9 Online
OpenStudy (chancemorris123):

Find the circumference of a circle whose area is /. A. B. C. D.

OpenStudy (chancemorris123):

OpenStudy (jdoe0001):

\(\bf \textit{area of a circle}=\pi r^2\qquad area=60\pi \qquad thus \\ \quad \\ 60\pi =\pi r^2\impliedby \textit{solve for "r"}\) what does that give you for "r"? or radius

OpenStudy (chancemorris123):

60=rsqure

OpenStudy (jdoe0001):

hmm rsquare?

OpenStudy (chancemorris123):

idk what r is

OpenStudy (jdoe0001):

\(\bf \textit{area of a circle}=\pi r^2\qquad area=60\pi \qquad thus \\ \quad \\ 60\pi =\pi r^2\implies \cfrac{60\cancel{\pi }}{\cancel{\pi }}=r^2\implies \sqrt{60}=\sqrt{r^2}\implies \sqrt{60}=r\)

OpenStudy (jdoe0001):

that was close though

OpenStudy (chancemorris123):

idk

OpenStudy (chancemorris123):

7.777

OpenStudy (jdoe0001):

so now that we know what "r" is let us use it in the circumference formula then \(\bf circumference=2\pi r\qquad \sqrt{60}=r\qquad then \\ \quad \\ circumference=2\pi \left( \sqrt{60} \right)\)

OpenStudy (jdoe0001):

and then you'd want to simplify that 60, see if you can squeeze something out of the radical

OpenStudy (chancemorris123):

30

OpenStudy (chancemorris123):

30 pie

OpenStudy (jdoe0001):

one may note that \(\huge \pi \ne pie\) but yours is tastier though

OpenStudy (chancemorris123):

so is it 30pie

OpenStudy (chancemorris123):

so is it 30 pie?

OpenStudy (jdoe0001):

\(\bf circumference=2\pi r\qquad \sqrt{60}=r\qquad then \\ \quad \\ circumference=2\pi \left( \sqrt{60} \right) \\ \quad \\ {\color{brown}{ 60\to 2\cdot 2\cdot 15\to 2^2\cdot 15 }}\qquad thus \\ \quad \\ 2\pi \left( \sqrt{60} \right)\implies 2\pi \left( \sqrt{{\color{brown}{ 2^2\cdot 15}}} \right)\implies 2\pi \sqrt{2^2}\sqrt{15}\)

OpenStudy (chancemorris123):

so its 2square root 5

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