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A wire when bent in the form of an equilateral triangle encloses an area of  121\sqrt{3}\; cm^2 . If the wire is bent in the form of a circle, find the area enclosed by the circle. \left ( \text{Use }\pi=\frac{22}{7} \right ).

 

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\text{Area of equilateral }\bigtriangleup =\frac{\sqrt{3}}{4}a^2

where a is a side of equilateral  \bigtriangleup.

Given : 

\text{Area of equilateral }\bigtriangleup =121\sqrt{3}\; cm^2

\Rightarrow \frac{\sqrt{3}}{4}a^2 =121\sqrt{3}

\Rightarrow a^2 =121\times 4

\Rightarrow a=\sqrt{121\times 4}

\Rightarrow a=11\times 2

\Rightarrow a=22\; cm

\text{Perimeter of circle }=\text{Perimeter of }\bigtriangleup

2\pi r=3a

2\times \frac{22}{7}\times r=3\times 22

r=\frac{3\times 22\times 7}{2\times 22}=\frac{21}{2}=10.5\; cm

r=10.5\; cm

\text{Area enclosed by circle }=\pi r^2

                                           =\frac{22}{7}\times 10.5\times 10.5

                                           =346.5\, cm^2

 

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Safeer PP

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