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Course: Geometry (OPS pilot) > Unit 1
Lesson 7: Perimeter, circumference, and area- Find a missing side length when given perimeter
- Find perimeter when a side length is missing
- Perimeter word problem: tables
- Perimeter word problem: skating rink
- Perimeter word problems
- Area & perimeter word problem: dog pen
- Area & perimeter word problem: table
- Comparing areas word problem
- Area and perimeter situations
- Represent rectangle measurements
- Area & perimeter of rectangles word problems
- Decomposing shapes to find area: grids
- Understand decomposing figures to find area
- Decomposing shapes to find area: add
- Decomposing shapes to find area: subtract
- Decompose figures to find area
- Drawing a quadrilateral on the coordinate plane example
- Drawing polygons with coordinates
- Area of a parallelogram on the coordinate plane
- Area and perimeter on the coordinate plane
- Coordinates of a missing vertex
- Example of shapes on a coordinate plane
- Dimensions of a rectangle from coordinates
- Coordinates of rectangle example
- Quadrilateral problems on the coordinate plane
- Quadrilateral problems on the coordinate plane
- Parallelogram on the coordinate plane
- Radius, diameter, circumference & π
- Labeling parts of a circle
- Radius, diameter, & circumference
- Radius and diameter
- Radius & diameter from circumference
- Relating circumference and area
- Circumference of a circle
- Area of a circle
- Area of a circle
- Partial circle area and arc length
- Circumference of parts of circles
- Area of parts of circles
- Circumference review
- Area of circles review
- Finding circumference of a circle when given the area
- Area of a shaded region
- Impact of increasing the radius
- Circumference and rotations
- Area and circumference of circles challenge
- Shaded areas
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Circumference review
Review the basics of circumference and try some practice problems.
What is circumference?
Circumference is the distance around the outside of a circle (its perimeter!).
Want a review of circle vocabulary terms (like pi, radius, and diameter)? Check out this video.
Finding circumference of a circle
To find the circumference of a circle, we can use either of the following formulas:
Want to know why these formulas work? Check out this article.
Example 1: Finding circumference when given diameter
Find the circumference of a circle with a diameter of .
The formula for the circumference of a circle that uses diameter is:
We can stop here and write our answer as . Or we can plug in for and multiply.
The circumference of the circle is units or units.
Example 2: Finding circumference when given radius
Find the circumference of a circle with a radius of .
The formula for the circumference of a circle that uses radius is:
We can stop here and write our answer as . Or we can plug in for and multiply.
The circumference of the circle is units or units.
Want to join the conversation?
- how to tell if your answer to circumference is correct(29 votes)
- To find area with circumference, you divide the circumference by pi, to get your diameter. Then, you find the radius by dividing the diameter by 2. You then multiply your radius by itself and multiply that product by pi.
Hope this Helps! :)(25 votes)
- why do we need to measure circles(21 votes)
- You don't really, but if you need to find your tire size, that's the way to do it. Also, a lot of math you won't really need for practicality, but you'll need it for high school which eventually leads up to college and your future job.(36 votes)
- Is the answer in the second practice question wrong?
My calculator said 9π is 28.27, not 28.26.
Ps: if it is wrong I don't see a way to report it.(14 votes)- If you use π then you will get 28.27.
If you use 3.14 then you will get 28.26.(24 votes)
- What should I do ,I need help(14 votes)
- You should watch all of the videos again; they will help!
If you are still having trouble, ask your teacher or your parent to help you!(6 votes)
- can we ban math from schools?(12 votes)
- No, maybe get better at math(11 votes)
- yall why are the questions from 4 years ago-(11 votes)
- The questions with the most votes are 4 years old, but if you go to the Sort by: and choose Recent, you will see questions that are 9, 10, and a month ago. Recent questions generally do not get many votes.(13 votes)
- Who made pie because whoever did must of been really smart(10 votes)
- No one really made it, Archimedes of Syracuse, was the first to calculate it.(11 votes)
- hey i need help i don't understand can someone help me this is on my finals(10 votes)
- and for area mutiply the radius by itself then multiply it by pie (3.14)(11 votes)
- why era there so much khan academy assinments(10 votes)
- im sorry it was my fault(9 votes)
- Hello, since the weather is terrible today, and my wifi is oging in and out, can someone explain this to me thanks!(12 votes)