Perimeter of Common Shapes

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The perimeter of a shape is found by adding up the length of all the sides. Find the perimeter of common shapes with help from a mathematics educator in this free video clip.

Part of the Video Series: Mathematics Equations & More
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Video Transcript

Hi, I'm Jimmy Chang and we're here to talk about perimeters of common shapes. Now one thing with common shapes, usually the shapes that come to mind are rectangles/squares, triangles and circles. Now let's talk about rectangles since squares work out the same way and basically what you've got to think about is the definition of perimeter is the distance around the shape itself. So let's just say you have a rectangle, let me just assign some numbers here, let's just say this is going to be 3, 3 and hypothetically 2, 2 and let's just say maybe inches as we would use for the unit as our final answer. Now what you want to think about is you can add the numbers around so 3 2 is 5, 5 3 is 8 and 8 2 is going to be 10. So let's just say the perimeter would be 10 let's just say inches. Now, when it comes to a triangle it works the same idea. So let's just say you have 3, 4 and let's just say 5 and let's just use you know if you want feet just to be different but you want to add all the numbers again together so 3 4 is 7, 7 5 is 12 so the perimeter is going to be 12, let's just say feet just as a demonstration. Now one thing you've got to think about though is that with circles they're a lot more unique because circles have their own formulas and we don't really say perimeters of circles, rather we would say circumference of a circle but that really means the same thing. So what you want to think about is suppose you have a circle that we're drawing here, now the formula for the circumference is C = 2 Pi R where R is the radius of the circle. So suppose you have the center here, suppose the radius is let's just say 2, so we'll just do inches just to keep it simple. What you want to do is to plug it in. You have C = 2 Pi X 2 and I'm going to leave the Pi as is and we have 2 X 2 is going to be 4 so C is going to be 4 Pi inches. Now Pi is approximately 3.14 but if you want a more specific decimal you can enter it on your calculator and that will give you a more definitive answer for circumference. So I'm Jimmy Chang and that's perimeter of common shapes.


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