1. Area and Perimeter of Similar Figures
Lesson #6
Pg. 147

2. What you will learn…
The perimeters of similar figures are related by the scale factor
The areas of similar figures are related by the square of the scale factor

3. Perimeter and Area of Similar Figures
Words - If figure B is similar to figure A by a scale factor, then the perimeter of B is equal to the perimeter of A times the scale factor
Symbols –
Models
Figure A
Figure B
Area
Words - If figure B is similar to figure A by a scale factor, then the Area of B is equal to the Area of A times the square of the scale factor
Perimeter of figure B
Perimeter of figure A
𝑆𝑐𝑎𝑙𝑒 𝐹𝑎𝑐𝑡𝑜𝑟
Area
of figure B
Area
of figure A
𝑆𝑐𝑎𝑙𝑒 𝐹𝑎𝑐𝑡𝑜𝑟 2

4. Perimeter Example
Two rectangles are similar. One has a length of 6in. And a perimeter of 24 in.. The other has a length of 7 in..
What is the perimeter of this rectangle?
Draw picture

5. Perimeter Example
Triangle LMN is similar to triangle PQR. If the perimeter of triangle LMN is 64 meters, what is the perimeter of triangle PQR?

6. Perimeter Example
In a scale drawing, the perimeter of the garden is 64 in.. The actual length of AB is 18ft..
What is the perimeter of the actual garden?
Always convert to same units
Find the scale factor
Find the perimeter of the actual garden

7. Perimeter Example
Two quilting squares are shown. The scale factor is 3 : 2.
What is the perimeter of square TUVW?

8. Area Example
The Eddington’s have a 5x8 ft. porch on the front of their house. They are building a similar poarch on the back with double (SF) the dimensions.
What is the area of the back porch?

9. Homework All: pg. 151-152 (1-7, 9, 10) Test Tuesday www.ixl.com Q13