Name __________________________________________ Date _________________
GUIDED NOTES: Perimeter and Area of Similar Polygons
THEOREM If the similarity ratio of two similar figures is a:b, then (1) the ratio of their perimeters is ____________ (2) the ratio of their areas is _______________ Example #1
The following trapezoids are similar.
Find the ratio of the perimeters:
Find the ratio of the areas (larger to smaller)
Example #2
Two similar polygons have corresponding sides in the ratio 5:7.
Find the ratio of the perimeters.
Find the ratio of their areas.
**IMPORTANT: When you know the area of one of the 2 similar polygons,
you can use a proportion to find the area of the other polygon.**
Example #3
Two pentagons are similar. The area of the smaller pentagon is about 27.5 𝑐𝑚! .
Find the area, A, of the larger regular pentagon.
Ratio of the corresponding sides:
Set up proportion:
Example #4
The areas of 2 similar triangles are 50 𝑐𝑚! and 98𝑐𝑚! . What is the similarity
ratio? What is the ratio of their perimeters?
Ratio of areas:
Simplify, if possible:
Take square root of both sides: