Question

Find the circumference of the circle that is within a square if the area of the square is 81 cm2.

Answer 1

Step-by-step explanation:

The area of a circle is πr²

The circumference of a circle is 2πr

According to the question ,

πr² = 81π

or, r² = 81

or, r = √(81)

or, r = ±9

But r=—9 is not acceptable .

so, r = 9 cm

Now,

Circumference of the circle is

2πr

= 2π * 9cm

= 18π cm

Answer 18π cm

Answer 2

${\huge{\star{\underbrace{\tt{\red{Answer}}}}}}{\huge{\star}}$

$\Large{\blue{\tt{\underline{\underline{Given \ :-}}}}}$

${\sf{❥ \ Area \ of \ square \ = \ 81cm²}}$

$\Large{\green{\tt{\underline{\underline{To \ find \ :-}}}}}$

${\sf{✿ \ Circumference \ of \ circle}}$

$\Large{\orange{\tt{\underline{\underline{Solution \ :-}}}}}$

${\tt{The \ side \ of \ square \ will \ be \ equal \ to }}\\ {\tt{diameter \ of \ circle}}$

${\bf{\large{✯Area \ of \ square \ = \ Side ²}}}$

${\sf{↣ \ 81 \ = \ Side²}}$

${\sf{↣ \ Side \ = \ \sqrt{81}}}$

${\sf{↣ \ Side \ = \ 9cm}}$

________________________________________

Now,

• Diameter of circle = 9cm

${\boxed{\sf \ ✯ \ Circumference \ of \ circle \ = \ \pi × diameter}}$

${\sf{\longmapsto \ Circumference \ = \ \frac{22}{7} × 9}}$

${\sf{\longmapsto \ Circumference \ = \ 28.28cm}}$

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