Perimeter and Circumference

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What is Perimeter?

Perimeter is the distance around the outside of a 2D
shape. To find the perimeter of any closed shape,
add the lengths of all sides.

3 + 4 + 5 = 12 cm

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Perimeter of a Rectangle

P = (2 × l) + (2 × w) l = length, w = width

P = (2 x 4) + (2 x 6)
P = 8 + 12
P = 20 ft

6 ft

4 ft

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Perimeter of Regular Polygons

Regular Polygon - all sides are the same length

P = n × s

n = number of sides, s = side length

2 in

P = 8 × 2
P = 16 in

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The Perimeter of the triangle is 14 units. What is
the length of the missing side?

P = s + s + s

14 = 5 + 5 + x

14 = 10 + x

-10 -10

_________________________

4 = x

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Parts of a Circle

Radius = the distance from the center of the circle to any
point on the circle (All radii in the same circle are the
same length.)

Diameter = the distance from one side of the circle to the
other through the center

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Circumference

Circumference = the distance around a circle

Circumference Formula

If you have radius:

If you have diameter:

C = 2 × π × r

C = π × d

C = 2 × π × r
C = 2 × 3.14 × 4
C = 25.12 m

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Circumference

Circumference = the distance around a circle

Circumference Formula

If you have radius:

If you have diameter:

C = 2 × π × r

C = π × d

C = π × d
C = 3.14 × 8
C = 25.12 m

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Note:

What is Pi?

Pi = π = 3.14