Area of Circles
Try VividMath Premium to unlock full access
Time limit: 0
Quiz summary
0 of 9 questions completed
Questions:
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
Information
–
You have already completed the quiz before. Hence you can not start it again.
Quiz is loading...
You must sign in or sign up to start the quiz.
You have to finish following quiz, to start this quiz:
Loading...
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- Answered
- Review
-
Question 1 of 9
1. Question
Find the area of the circle
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (78.5, 78.6) `cm^2`
Hint
Help VideoCorrect
Well Done!
Incorrect
Area of a Circle Formula
`\text(Area)=pi times``\text(radius)^2`Given Lengths
`\text(radius)=5`
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 ``5^2` Plug in the known values `=` `3.14 times 25` Evaluate `=` `78.5 cm^2` The given measurements are in centimetres, so the area is measured as square centimetres`\text(Area)=78.5 cm^2`The answer will depend on which `pi` you use.In this solution we used: `pi=3.14`.Using Answer `pi=3.14` `78.5 cm^2` `pi=3.141592654` `78.5 cm^2` `pi=(22)/(7)` `78.6 cm^2` -
Question 2 of 9
2. 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
Help VideoCorrect
Nice Job!
Incorrect
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 3 of 9
3. Question
Find the area of the circle
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (346.2, 346.4, 346.5) `m^2`
Correct
Great Work!
Incorrect
Area of a Circle Formula
`\text(Area)=pi times``\text(radius)^2`Given Lengths
`\text(diameter)=21`
First, find the radius of the circle. Note that the radius is half of the diameter`\text(radius)` `=` $$\frac{\color{#00880a}{\text{diameter}}}{2}$$ `=` $$\frac{\color{#00880a}{\text{21}}}{2}$$ `\text(radius)` `=` `10.5` 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 ``10.5^2` Plug in the known values `=` `3.14 times 110.25` Evaluate `=` `346.185` `=` `346.2 m^2` Rounded to `1` decimal place The given measurements are in metres, so the area is measured as square metres`\text(Area)=346.2 m^2`The answer will depend on which `pi` you use.In this solution we used: `pi=3.14`.Using Answer `pi=3.14` `346.2 m^2` `pi=3.141592654` `346.4 m^2` `pi=(22)/(7)` `346.5 m^2` -
Question 4 of 9
4. 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 5 of 9
5. Question
Find the area of the Circle
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (149.5, 149.6) `km^2`
Correct
Keep Going!
Incorrect
Area of a Circle Formula
`\text(Area)=pi times``\text(radius)^2`Given Lengths
`\text(diameter)=13.8`
First, find the radius of the circle
Note that the radius is half of the diameter`\text(radius)` `=` $$\frac{\color{#00880a}{\text{diameter}}}{2}$$ `=` $$\frac{\color{#00880a}{\text{13.8}}}{2}$$ `\text(radius)` `=` `6.9` 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 ``6.9^2` Plug in the known values `=` `3.14 times 47.61` Evaluate `=` `149.4954` `=` `149.5 km^2` Rounded to `1` decimal place The given measurements are in kilometres, so the area is measured as square kilometres`\text(Area)=149.5 km^2`The answer will depend on which `pi` you use.In this solution we used: `pi=3.14`.Using Answer `pi=3.14` `149.5 km^2` `pi=3.141592654` `149.6 km^2` `pi=(22)/(7)` `149.6 km^2` -
Question 6 of 9
6. 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 7 of 9
7. Question
Find the area of the orange-shaded region.
The given measurements are in centimetres.Round your answer to `1` decimal place.`pi=3.14`- `\text(Area )=` (103.7, 103.6) `cm^2`
Hint
Help VideoCorrect
Correct!
Incorrect
Area of a Circle Formula
`\text(Area)=pi xx``\text(radius)^2`Given Lengths
`\text(radius)` (Whole Circle)`=7``\text(thickness)` (Shaded Region)`=3`
First, solve for the area of the Whole CircleUse `pi=3.14` See `pi` explained`\text(Area)``\text(Whole Circle)` `=` `pi xx``\text(radius)^2` `=` `3.14 xx``7^2` `\text(Area)` `=` `153.86 cm^2` 
Find the radius of the Inner Circle by subtracting the thickness of the shaded region from the radius of the Whole Circle.`\text(radius)``\text(Inner Circle)` `=` `\text(radius)``-``\text(thickness)` `=` `7``-``3` `=` `4 cm` 
Next, find the area of the Inner Circle`\text(Area)``\text(Inner Circle)` `=` `pi xx``\text(radius)^2` `=` `3.14 times ``4^2` `\text(Area)` `=` `50.24 cm^2` 
Finally, subtract the area of the Inner Circle from the area of the Whole Circle`\text(Final Area)` `=` `153.86``-``50.24` `=` `103.62` `=` `103.6 cm^2` Rounded to `1` decimal place The given measurements are in centimetres, so the area is measured as square centimetres`\text(Area)=103.6 cm^2`The answer will depend on which `pi` you use.In this solution we used: `pi=3.14`.Using Answer `pi=3.14` `103.6 cm^2` `pi=3.141592654` `103.7 cm^2` `pi=(22)/(7)` `103.7 cm^2` -
Question 8 of 9
8. Question
Find the area of the yellow-shaded region.
Round your answer to `1` decimal placeUse `pi=3.14`- `\text(Area )=` (50.2, 50.3) `cm^2`
Hint
Help VideoCorrect
Fantastic!
Incorrect
Area of a Semicircle Formula
`\text(Area)=1/2 xx pi xx``\text(radius)^2`Given Lengths
`\text(radius)` (Whole Semicircle)`=9``\text(thickness)` (Shaded Region)`=2`
First, solve for the area of the Whole SemicircleUse `pi=3.14` See `pi` explained`\text(Area)``\text(Whole Semicircle)` `=` `1/2 xx pi xx``\text(radius)^2` `=` `1/2 xx 3.14 xx``9^2` `\text(Area)` `=` `127.17 cm^2` 
Find the radius of the Inner Semicircle by subtracting the thickness of the shaded region from the radius of the Whole Semicircle.`\text(radius)``\text(Inner Semicircle)` `=` `\text(radius)``-``\text(thickness)` `=` `9``-``2` `=` `7 cm` 
Next, find the area of the Inner Semicircle`\text(Area)``\text(Inner Semicircle)` `=` `1/2 xx pi xx``\text(radius)^2` `=` `1/2 xx 3.14 times ``7^2` `\text(Area)` `=` `76.93 cm^2` 
Finally, subtract the area of the Inner Semicircle from the area of the Whole Semicircle`\text(Final Area)` `=` `127.17``-``76.93` `=` `50.24` `=` `50.2 cm^2` Rounded to `1` decimal place The given measurements are in centimetres, so the area is measured as square centimetres`\text(Area)=50.2 cm^2`The answer will depend on which `pi` you use.In this solution we used: `pi=3.14`.Using Answer `pi=3.14` `50.2 cm^2` `pi=3.141592654` `50.3 cm^2` `pi=(22)/(7)` `50.3 cm^2` -
Question 9 of 9
9. 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
Help VideoCorrect
Fantastic
Incorrect
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`