Perimeter, Circumference, and Area

Learning Target: I can find the perimeter, circumference, and area of basic shapes.

The perimeter of a polygon is the sum of the lengths of its sides.

The area of a polygon is the number of square units it encloses.

The perimeter of a circle is called its circumference.

How could we find the area and perimeter of a square?

Area:s2

Perimeter: 4s

s

s

How could we find the area and perimeter of a triangle?

Area: (1/2)bh

Perimeter:add the sides together base (b)

height (h)

How could we find the area and perimeter of a rectangle?

Area: lw

Perimeter: 2l+2w

lenght (l)

width (w)

How could we find the area and circumference of a circle?

Area: πr2

Circumference: 2rπ

radius (r)

Remember diameter=2 radius

Finding Circumference

What is the circumference of the circle in terms of π?

What is the circumference of the circle to the nearest tenth?

15 in

diameter=15, so radius=7.5

circumference=2rπ=2(15)π=30π

Try these:

What is the circumference of a circle with radius 24 m in terms of π?circumference=2rπ=2(24)π=48π

What is the circumference of a circle with diameter 24 to the nearest tenth?circumference=2rπ=2(12)π=24(3.14)=75.4

What is the area of the figure? All angles are right angles.

3 cm

9 cmYou can cut the picture into 6 congruent squares. Area of one square is (6)(6)=36.Since there are 6 squares (6)(36)=216

What is the area of the figure? All angles are right angles.

4 ft

12 ft

Cut the figure into a triangle on top and rectangle on bottom.Area of the triangle is (1/2)(8)(4)=16Area of the rectangle is (4)(12)=4816+48=64