http://www.ck12.org Chapter 10. Perimeter and Area
10.3 Areas of Similar Polygons
Learning Objectives
- Understand the relationship between the scale factor of similar polygons and their areas.
- Apply scale factors to solve problems about areas of similar polygons.
Review Queue
- Are two squares similar? Are two rectangles?
- Find the scale factor of the sides of the similar shapes. Both figures are squares.
- Find the area of each square.
- Find the ratio of the smaller square’s area to the larger square’s area. Reduce it. How does it relate to the scale
factor?
Know What?One use of scale factors and areas is scale drawings. This technique takes a small object, like the
handprint to the right, divides it up into smaller squares and then blows up the individual squares. In this Know
What? you are going to make a scale drawing of your own hand. Either trace your hand or stamp it on a piece of
paper. Then, divide your hand into 9 squares, like the one to the right, probably 2in× 2 in. Take a larger piece of
paper and blow up each square to be 6in× 6 in(meaning you need at least an 18 in square piece of paper). Once
you have your 6in× 6 insquares drawn, use the proportions and area to draw in your enlarged handprint.