Question

5. Nidhi divides a circular disc of radius 21 cm in two equal parts. What is the perimeu
semi-circular shape disc? Take n = )
​

Answer 1

Step-by-step explanation:

$perimeter \: of \: a \: circle = 2\pi \: r \\ semiperimeter = \pi \: r \\ = \pi \times 21cm \\ = \frac{22}{7} \times 21cm \\ = 22 \times 3cm \\ = 66cm$

therefore semi perimeter is 66cm

Answer 2

The perimeter of semi-circular shape disc is 66 cm.

Explanation:

We know that the circumference of circle = $2\pi r$ , where r= radius of the circle.

Since semicircle is half of the circle , then the circumference of the semi-circle =   (circumference of circle ) ÷ 2

$=\pi r$

For r= 21 cm

Circumference of the semicircle = $\pi (21)= (\dfrac{22}{7})(21)=66\ cm$

[here $\pi=\dfrac{22}{7}$]

Therefore , the perimeter of semi-circular shape disc is 66 cm.

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