Areas of Circles 2
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Question 1 of 4
1. Question
Find the area of the Circle
Round your answer to `1` decimal placeUse `pi=3.141592654`- `\text(Area )=` (254.5, 254.3, 254.6) `mm^2`
Hint
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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
2. Question
Find the area of the Circle
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (452.2, 452.4, 452.6) `m^2`
Correct
Correct!
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
3. Question
Find the area of the Circle
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (12.6) `cm^2`
Correct
Fantastic!
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
4. Question
Find the area of the yellow-shaded region.
Round your answer to `2` decimal placesUse `pi=3.141592654`- `\text(Area )=` (96.21, 96.16, 96.25) `m^2`
Hint
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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 SemicircleUse `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`