Download 7.1 Notes - Garnet Valley School District

Geometry B
Date: _____________
7.1 Ratios in Similar Polygons
Objective: To identify similar polygons and apply their properties to solve problems
Definition:
 Similar Polygons: ___________________________________________________________
o Corresponding Angles are ______________________
o Corresponding Sides are _______________________
o The symbol for similarity is __________
Ex. 1: Describing Similar Polygons
Identify the pairs of corresponding angles and sides in the similar triangles below.
Angles: ____________
____________
____________
Sides:
____________
____________
____________
Similarity Statement: __________________________
Practice:
Angles: _________ __________
___________
Sides:
__________
__________ __________
0.5
Similarity Statement: __________________________

Similarity Ratio (or Scale Factor): _______________________________________________
Similarity Ratio of ΔABC to ΔDEF: ___________________________
Similarity Ratio of ΔDEF to ΔABC: ___________________________
Ex. 2: Writing Similarity Ratios
Write the similarity ratio for the two sets of triangles from Example 1.
Similarity Ratio of ΔABC to ΔJGH: ________
Similarity Ratio of ΔMNP to ΔTQR: ________
How to tell if two polygons are similar:
 Are all of the angles congruent?
 Are the sides proportional? Order sides from least to greatest and match corresponding sides
together. Check to see if they all have the same similarity ratio.
 If you answered “yes” to both of those questions, the polygons are similar.
Ex. 2: Identifying Similar Polygons
Determine whether the two polygons are similar. If yes, write a similarity statement and the scale
factor.
a. ABCD and EFGH are both rectangles.
b.
Practice: Determine whether the two polygons are similar. If yes, write a similarity statement and
the scale factor.
Ex. 3: Finding Missing Sides of Similar Polygons
The polygons below are similar. Use a proportion to find the missing value.
a.
b.
Ex. 4: Similarity Application
A boxcar has the dimensions shown. A model of the boxcar is 1.25 in. wide. Find the length of
the model to the nearest inch
HW: 7.1 Worksheet