GeometryChapter 1 - Essentials of GeometrySection 1.7 - Find perimeter, circumference, and area

What the student should get from this:1. Apply formulas for perimeter, area, and circumference

What is perimeter?

What is the perimeter of the figure at the right?(assume right angles)

For rectangular figures p = 2l + 2w

Example:

For triangular figures... add up the sides.!! ! Example:

For circles, use C = 2!r or C = !d

Example:

Another Example:

What is the radiusof the circle with circumference of 15 cm?

46 ft

38 ft

26 ft

14.3 ft

5.8 ft6 cm

6 cm6 5cm

15 cm

15 cm

Letʼs talk area!

The formula for the area of a rectangle is A = bh or area equals base times height.

Example:

There are several area formulas for triangles... (Memorize them!)

Find the perimeter of each figure:

12 7 ft

7 3 ft

A =12bh A =

s2 34

for equilateral triangles only

Example: to use this formula, you must know the length of the base and the height of the triangle

height always makes a right angle with the base

4 2m

3 2m

7 in.

9 in.

10 in.

6 in. 6 in.

6 in.

Lastly, the area of a circle is given by A = !r2 .

Examples: find the area of each...

A couple more things:

The area of a triangle is 282.5 sq. ft. The height is 22.6 ft. How long is the base?

The perimeter of a rectangular fountain is 120 3 ft . The base is 40 feet. How wide is the fountain?

The length of a rectangular flower bed is 3 times the width. The area is 300 square feet. What are the dimensions of the flower bed?

Assignment: p.52 #s 3-17 odd, 27-29 all, 32, 46, 47. Show work. Draw all pictures. Due next period.

8 cm6 6m

circumference is 14π