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Geometry Chapter 1 - Essentials of Geometry Section 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?

38 ft

What is the perimeter of the figure at the right? (assume right angles) 26 ft

46 ft For rectangular figures p = 2l + 2w 14.3 ft Example: 5.8 ft

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

6 cm !


6 5cm For circles, use C = 2! r or C = ! d Example: 15 cm

Another Example: What is the radius of the circle with circumference of 15 cm?

15 cm

6 cm

Let始s talk area! The formula for the area of a rectangle is A = bh or area equals base times height. Example:

7 3 ft

12 7 ft There are several area formulas for triangles... (Memorize them!)


1 bh 2


s2 3 4

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

3 2m

4 2m

Find the perimeter of each figure: 10 in. 6 in.

6 in.

7 in. 9 in. 6 in.

Lastly, the area of a circle is given by A = ! r 2 . Examples: find the area of each...

8 cm

6 6m

circumference is 14Ď€

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.


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