Name: Perimeter of a Closed Semicircular Figure
Uploaded: 2019-07-19
Duration: 2 min 24 s
Description: We know how to calculate the circumference or perimeter of a circle. Let’s watch how to calculate the perimeter of a closed semicircular figure in this video.

Question

Find the circumference and area of the following circles. Use $3.14$ for the value of $π$ , and round your answers to the nearest hundredth.

Accepted Answer

For the following circle, we find circumference and area one by one.

First, we have to know the formula of circumference and area of a circle.

The circumference of a circle is calculated using the formula $C = 2 π r$ .

The area of a circle is calculated using the formula $A = π r^{2}$ .

Here, r is the radius of a circle.

Now, we find the circumference and area of a circle.

For, the first circle:

From fig. we come to know that radius(r) is $4 cm$ .

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 4 Circumference of circle = 25.12 cm$

Now, we find the area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(4)}^{2} Area of circle = 3.14 \times 4 \times 4 Area of circle = 50.24 {cm}^{2}$

For the second circle:

From fig. we come to know that radius(r) is $6.2 in$ .

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 6.2 Circumference of circle = 38.94 i n$

Now, we find the area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(6.2)}^{2} Area of circle = 3.14 \times 6.2 \times 6.2 Area of circle = 120.70 {in}^{2}$

For the third circle

From fig. we come to know that diameter is 18ft.

So, $R a d i u s (r) = \frac{D i a m e t e r}{2} = \frac{18}{2} = 9 f t$

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 9 Circumference of circle = 56.52 ft$

Now, we find the area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(9)}^{2} Area of circle = 3.14 \times 9 \times 9 Area of circle = 254.34 {ft}^{2}$

For forth circle

From fig. we come to know that radius(r) is $11.5 m$ .

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 11.5 Circumference of circle = 72.22 m$

Now, we find area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(11.5)}^{2} Area of circle = 3.14 \times 11.5 \times 11.5 Area of circle = 415.27 m^{2}$

For the fifth circle

From fig. we come to know that diameter is $5.7 cm$

So, $R a d i u s (r) = \frac{D i a m e t e r}{2} = \frac{5.7}{2} = 2.85 c m$

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 2.85 Circumference of circle = 17.90 cm$

Now, we find the area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(2.85)}^{2} Area of circle = 3.14 \times 2.85 \times 2.85 Area of circle = 25.50 {cm}^{2}$

For the sixth circle

From fig. we come to know that radius(r) is $0.75 i n$ .

First, we find the circumference.

$C i r c u m f e r e n c e o f c i r c l e = 2 πr Circumference of circle = 2 \times 3.14 \times 0.75 Circumference of circle = 4.71 in$

Now, we find the area.

$A r e a o f c i r c l e = {πr}^{2} Area of circle = 3.14 \times {(0.75)}^{2} Area of circle = 3.14 \times 0.75 \times 0.75 Area of circle = 1.77 {in}^{2}$

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