Perimeter

Rectangles, Squares, and Triangles

Perimeter

Measures the distance around the edge of any flat object.

To find the perimeter of any figure, ADD the lengths of its sides.

What is a rectangle?

A rectangle has:

4 sides

4 square corners or right angles

Opposite sides are of equal lengths

Opposite sides are directly across from each other

To find the perimeter of a rectangle:

18

15

Use the formula

P= 2 x length + 2 x widthP= 2 x 18 + 2 x 15P= 36 + 30= 66

Or …….You can always add the sides.P= 18 + 18 +15 +15= 66

What is a square?

A square has:

4 equal sides 4 right angles

To find the perimeter of a square:

Use the formula:

P = 4 x side P = 4 x 3 = 12

3

3

Or . . . . You can add the sides.

P = 3 + 3 + 3 + 3 = 12

What is a triangle?

A triangle has 3 sides.

All triangles may not look the same, but they all have 3 sides.

To find the perimeter of a triangle:

Use the formula:

P = side + side + side P = 6 + 6 + 4 = 16

6 6

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Circumference of a Circle

The perimeter, or the distance around a

circle, is called the circumference.

Circumference of a Circle

To find the circumference of a circle, you need to know either the diameter or radius of the circle.

The diameter of a circle is a line segment drawn through the center of the circle with endpoints on the circle.

Diameter

The radius is a line segment connecting the circle’s center to a point on the circle. The length of the radius is one-half the length of the diameter.

Radius

Diameter

The formula for finding circumference (C) is C = pi x diameter.

The value of pi is about 3.14, so the formula for finding the circumference of a circle is C = 3.14 x diameter.

Find the circumference of the circle. C = pi x diameter C = 3.14 x 4= 12.56

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