Question

find the circumference of a circle whose area is 4 times the area of circle with diameter 21 CM

Answer 1

Answer:

$\red{Circumference \:of \:the \:circle }\green{=1386\:cm }$

Step-by-step explanation:

$Let \: the \: diameter \:of \:a \: circle (d) = 21\:cm$

$Circumference \:of \:the \:circle (C) \\= 4 \times (Area \:of \:the \:circle )\\= 4\times \pi \frac{d^{4}}{4} \\= \pi d^{2}\\= \frac{22}{7} \times 21^{2}\\= 22\times 3 \times 21 \\= 1386\:cm$

Therefore.,

$\red{Circumference\:of\:the \:circle }\green{=1386\:cm }$

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