Question

find the area and circumference of a circle of radius 21 cm​

Answer 1

Answer:

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Step-by-step explanation:

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Answer 2

Given :-

• A circle whose radius is 21 cm.

To Find :-

• What is the circumference and area.

Formula Used :-

✧ To find circumference of a circle we know that,

${\red{\boxed{\large{\bold{Circumference\: of\: circle\: =\: 2{\pi}r}}}}}$

✧ To find area of the circle we know that,

${\red{\boxed{\large{\bold{Area\: of\: circle\: =\: {\pi}{r}^{2}}}}}}$

Solution :-

➤ To find circumference of the circle

• Radius = 21 cm

According to the question by using the formula we get,

⇒ $\sf Circumference =\: 2 \times \dfrac{22}{7} \times 21$

⇒ $\sf Circumference =\: 2 \times \dfrac{22}{\cancel{7}} \times {\cancel{21}}$

⇒ $\sf Circumference =\: 2 \times 22 \times 3$

⇒ $\sf Circumference =\: 44 \times 3$

➠ $\sf\bold{\blue{Circumference =\: 132\: cm}}$

$\therefore$The circumference of the circle is 132 cm .

➤ To find area of the circle,

• Radius = 21 cm

According to the question by using the 

formula we get,

↦ $\sf Area =\: \dfrac{22}{7} \times {(21)}^{2}$

↦ $\sf Area =\: \dfrac{22}{7} \times 21 \times 21$

↦ $\sf Area =\: \dfrac{22}{7} \times 441$

↦ $\sf Area =\: \dfrac{22}{\cancel{7}} \times {\cancel{441}}$

↦ $\sf Area =\: 22 \times 63$

➦ $\sf\bold{\purple{Area =\: 1386 c{m}^{2}}}$

$\therefore$ The area of the circle is 1386 cm² .

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