Areas of Circles 2

Question 1 of 4

Find the area of the Circle

Round your answer to

$1$ decimal place

Use

$pi=3.141592654$

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

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Area of a Circle Formula

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

Given Lengths

$\text(diameter)=18$

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

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

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

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

Finally, solve for the area using the formula:

$A=pi$ $r^2$

Use

$pi=3.141592654$ See

$pi$ explained

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

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

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

The answer will depend on which

$pi$ you use.

In this solution we used:

$pi=3.141592654$ .

Using	Answer
$pi=3.141592654$	$254.5 mm^2$
$pi=3.14$	$254.3 mm^2$
$pi=(22)/(7)$	$254.6 mm^2$

Question 2 of 4

Find the area of the Circle

Round your answer to

$1$ decimal place

Use

$pi=3.14$

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

Incorrect

Area of a Circle Formula

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

Given Lengths

$\text(diameter)=24$

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

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

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

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

Finally, solve for the area using the formula:

$A=pi$ $r^2$

Use

$pi=3.14$ See

$pi$ explained

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

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

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

The answer will depend on which

$pi$ you use.

In this solution we used:

$pi=3.14$ .

Using	Answer
$pi=3.14$	$452.2 m^2$
$pi=3.141592654$	$452.4 m^2$
$pi=(22)/(7)$	$452.6 m^2$

Question 3 of 4

Find the area of the Circle

Round your answer to

$1$ decimal place

Use

$pi=3.14$

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

Incorrect

Area of a Circle Formula

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

Given Lengths

$\text(diameter)=4$

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

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

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

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

Finally, solve for the area using the formula:

$A=pi$ $r^2$

Use

$pi=3.14$ See

$pi$ explained

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

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

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

The answer will depend on which

$pi$ you use.

In this solution we used:

$pi=3.14$ .

Using	Answer
$pi=3.14$	$12.6 cm^2$
$pi=3.141592654$	$12.6 cm^2$
$pi=(22)/(7)$	$12.6 cm^2$

Question 4 of 4

Find the area of the yellow-shaded region.

Round your answer to

$2$ decimal places

Use

$pi=3.141592654$

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

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Area of a Semicircle Formula

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

Given Lengths

$\text(radius)$ (Larger Semicircle)

$=7$

$\text(diameter)$ (Smaller Semicircle)

$=7$

First, solve for the area of the Larger Semicircle

Use

$pi=3.141592654$ See

$pi$ explained

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

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

$7$

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

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

Next, find the area of the Smaller Semicircle

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

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

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

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

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

The answer will depend on which

$pi$ you use.

In this solution we used:

$pi=3.141592654$ .

Using	Answer
$pi=3.141592654$	$96.21 m^2$
$pi=3.14$	$96.16 m^2$
$pi=(22)/(7)$	$96.25 m^2$

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