Areas of Circles 2

Question 1 of 4

Find the area of the Circle

Round your answer to

1

$1$ decimal place

Use

π = 3.141592654

$pi=3.141592654$

$Area =$ $\text(Area )=$ (254.5, 254.3, 254.6) $m m^{2}$ $mm^2$

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Area of a Circle Formula

Area = π \times

$\text(Area)=pi times$ ${radius}^{2}$ $\text(radius)^2$

Given Lengths

diameter = 18

$\text(diameter)=18$

First, find the radius of the circle. Note that the radius is half of the diameter.

$radius$ $\text(radius)$	$=$ $=$	$\frac{\color{#00880a}{\text{diameter}}}{2}$

	$=$ $=$	$\frac{\color{#00880a}{\text{18}}}{2}$

$radius$ $\text(radius)$	$=$ $=$	$9$ $9$

Finally, solve for the area using the formula:

A = π

$A=pi$ $r^{2}$ $r^2$

Use

π = 3.141592654

$pi=3.141592654$ See

π

$pi$ explained

$Area$ $\text(Area)$	$=$ $=$	$π \times$ $pi times$ ${radius}^{2}$ $\text(radius)^2$	Area of a Circle Formula
	$=$ $=$	$3.141592654 \times$ $3.141592654 times$ $9^{2}$ $9^2$	Plug in the known values
	$=$ $=$	$3.141592654 \times 81$ $3.141592654 times 81$	Evaluate
	$=$ $=$	$254.46900$ $254.46900$
	$=$ $=$	$254.5 m m^{2}$ $254.5 mm^2$	Rounded to $1$ $1$ decimal place

The given measurements are in millimetres, so the area is measured as square millimetres

Area = 254.5 m m^{2}

$\text(Area)=254.5 mm^2$

The answer will depend on which

π

$pi$ you use.

In this solution we used:

π = 3.141592654

$pi=3.141592654$ .

Using	Answer
$π = 3.141592654$ $pi=3.141592654$	$254.5 m m^{2}$ $254.5 mm^2$
$π = 3.14$ $pi=3.14$	$254.3 m m^{2}$ $254.3 mm^2$
$π = \frac{22}{7}$ $pi=(22)/(7)$	$254.6 m m^{2}$ $254.6 mm^2$

Question 2 of 4

Find the area of the Circle

Round your answer to

1

$1$ decimal place

Use

π = 3.14

$pi=3.14$

$Area =$ $\text(Area )=$ (452.2, 452.4, 452.6) $m^{2}$ $m^2$

Incorrect

Area of a Circle Formula

Area = π \times

$\text(Area)=pi times$ ${radius}^{2}$ $\text(radius)^2$

Given Lengths

diameter = 24

$\text(diameter)=24$

First, find the radius of the circle. Note that the radius is half of the diameter

$radius$ $\text(radius)$	$=$ $=$	$\frac{\color{#00880a}{\text{diameter}}}{2}$

	$=$ $=$	$\frac{\color{#00880a}{\text{24}}}{2}$

$radius$ $\text(radius)$	$=$ $=$	$12$ $12$

Finally, solve for the area using the formula:

A = π

$A=pi$ $r^{2}$ $r^2$

Use

π = 3.14

$pi=3.14$ See

π

$pi$ explained

$Area$ $\text(Area)$	$=$ $=$	$π \times$ $pi times$ ${radius}^{2}$ $\text(radius)^2$	Area of a Circle Formula
	$=$ $=$	$3.14 \times$ $3.14 times$ $12^{2}$ $12^2$	Plug in the known values
	$=$ $=$	$3.14 \times 144$ $3.14 times 144$	Evaluate
	$=$ $=$	$452.16$ $452.16$
	$=$ $=$	$452.2 m^{2}$ $452.2 m^2$	Rounded to $1$ $1$ decimal place

The given measurements are in metres, so the area is measured as square metres

Area = 452.2 m^{2}

$\text(Area)=452.2 m^2$

The answer will depend on which

π

$pi$ you use.

In this solution we used:

π = 3.14

$pi=3.14$ .

Using	Answer
$π = 3.14$ $pi=3.14$	$452.2 m^{2}$ $452.2 m^2$
$π = 3.141592654$ $pi=3.141592654$	$452.4 m^{2}$ $452.4 m^2$
$π = \frac{22}{7}$ $pi=(22)/(7)$	$452.6 m^{2}$ $452.6 m^2$

Question 3 of 4

Find the area of the Circle

Round your answer to

1

$1$ decimal place

Use

π = 3.14

$pi=3.14$

$Area =$ $\text(Area )=$ (12.6) $c m^{2}$ $cm^2$

Incorrect

Area of a Circle Formula

Area = π \times

$\text(Area)=pi times$ ${radius}^{2}$ $\text(radius)^2$

Given Lengths

diameter = 4

$\text(diameter)=4$

First, find the radius of the circle
Note that the radius is half of the diameter

$radius$ $\text(radius)$	$=$ $=$	$\frac{\color{#00880a}{\text{diameter}}}{2}$

	$=$ $=$	$\frac{\color{#00880a}{\text{4}}}{2}$

$radius$ $\text(radius)$	$=$ $=$	$2$ $2$

Finally, solve for the area using the formula:

A = π

$A=pi$ $r^{2}$ $r^2$

Use

π = 3.14

$pi=3.14$ See

π

$pi$ explained

$Area$ $\text(Area)$	$=$ $=$	$π \times$ $pi times$ ${radius}^{2}$ $\text(radius)^2$	Area of a Circle Formula
	$=$ $=$	$3.14 \times$ $3.14 times$ $2^{2}$ $2^2$	Plug in the known values
	$=$ $=$	$3.14 \times 4$ $3.14 times 4$	Evaluate
	$=$ $=$	$12.56$ $12.56$
	$=$ $=$	$12.6 c m^{2}$ $12.6 cm^2$	Rounded to $1$ $1$ decimal place

The given measurements are in centimetres, so the area is measured as square centimetres

Area = 12.6 c m^{2}

$\text(Area)=12.6 cm^2$

The answer will depend on which

π

$pi$ you use.

In this solution we used:

π = 3.14

$pi=3.14$ .

Using	Answer
$π = 3.14$ $pi=3.14$	$12.6 c m^{2}$ $12.6 cm^2$
$π = 3.141592654$ $pi=3.141592654$	$12.6 c m^{2}$ $12.6 cm^2$
$π = \frac{22}{7}$ $pi=(22)/(7)$	$12.6 c m^{2}$ $12.6 cm^2$

Question 4 of 4

Find the area of the yellow-shaded region.

Round your answer to

2

$2$ decimal places

Use

π = 3.141592654

$pi=3.141592654$

$Area =$ $\text(Area )=$ (96.21, 96.16, 96.25) $m^{2}$ $m^2$

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Area of a Semicircle Formula

Area = \frac{1}{2} \times π \times

$\text(Area)=1/2 xx pi xx$ ${radius}^{2}$ $\text(radius)^2$

Given Lengths

radius

$\text(radius)$ (Larger Semicircle)

= 7

$=7$

diameter

$\text(diameter)$ (Smaller Semicircle)

= 7

$=7$

First, solve for the area of the Larger Semicircle

Use

π = 3.141592654

$pi=3.141592654$ See

π

$pi$ explained

$Area$ $\text(Area)$ _{$Larger Semicircle$ $\text(Larger Semicircle)$}	$=$ $=$	$\frac{1}{2} \times π \times$ $1/2 xx pi xx$ ${radius}^{2}$ $\text(radius)^2$
	$=$ $=$	$\frac{1}{2} \times 3.141592654 \times$ $1/2 xx 3.141592654 xx$ $7^{2}$ $7^2$
$Area$ $\text(Area)$	$=$ $=$	$76.96902 m^{2}$ $76.96902 m^2$

We can see on the image that the diameter of the Smaller Semicircle is

7

$7$

We will use that to solve for the radius of the Smaller Semicircle, which is half of its diameter

$radius$ $\text(radius)$ _{$Smaller Semicircle$ $\text(Smaller Semicircle)$}	$=$ $=$	$\frac{\color{#00880a}{\text{diameter}}}{2}$
	$=$ $=$	$\frac{\color{#00880a}{\text{7}}}{2}$
	$=$ $=$	$3.5 m$ $3.5 m$

Next, find the area of the Smaller Semicircle

$Area$ $\text(Area)$ _{$Smaller Semicircle$ $\text(Smaller Semicircle)$}	$=$ $=$	$\frac{1}{2} \times π \times$ $1/2 xx pi xx$ ${radius}^{2}$ $\text(radius)^2$
	$=$ $=$	$\frac{1}{2} \times 3.141592654 \times$ $1/2 xx 3.141592654 times$ ${3.5}^{2}$ $3.5^2$
$Area$ $\text(Area)$	$=$ $=$	$19.24225 m^{2}$ $19.24225 m^2$

Finally, add the area of the Larger Semicircle and the area of the Smaller Semicircle

$Final Area$ $\text(Final Area)$	$=$ $=$	$76.96902$ $76.96902$ $+$ $+$ $19.24225$ $19.24225$
	$=$ $=$	$96.21127$ $96.21127$
	$=$ $=$	$96.21 m^{2}$ $96.21 m^2$	Rounded to $2$ $2$ decimal places

The given measurements are in metres, so the area is measured as square metres

Area = 96.21 m^{2}

$\text(Area)=96.21 m^2$

The answer will depend on which

π

$pi$ you use.

In this solution we used:

π = 3.141592654

$pi=3.141592654$ .

Using	Answer
$π = 3.141592654$ $pi=3.141592654$	$96.21 m^{2}$ $96.21 m^2$
$π = 3.14$ $pi=3.14$	$96.16 m^{2}$ $96.16 m^2$
$π = \frac{22}{7}$ $pi=(22)/(7)$	$96.25 m^{2}$ $96.25 m^2$

Areas of Circles 2

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Quiz summary

Information

1. Question

Hint

Nice Job!

Area of a Circle Formula

Given Lengths

2. Question

Correct!

Area of a Circle Formula

Given Lengths

3. Question

Fantastic!

Area of a Circle Formula

Given Lengths

4. Question

Hint

Area of a Semicircle Formula

Given Lengths

Quizzes