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# Geometry Warm-Up 1/13/11 - PowerPoint PPT Presentation

Geometry Warm-Up 1/13/11. In a triangle, the ratio of the measures of three sides is 3:4:5, and the perimeter is 42 feet. Find the measure of the longest side of the triangle.

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Presentation Transcript

In a triangle, the ratio of the measures of three sides is 3:4:5, and the perimeter is 42 feet. Find the measure of the longest side of the triangle.

A boxcar on a train has a length of 40 feet and a width of 9 feet. A scale model is made with a length of 16 inches. Find the width of the model.

### Sec. 7.2: Similar Polygons

Geometry

January 13, 2011

Similar – same shape but different size

A

ABCD ~ GEFH

• Polygons are similar when

• Their corresponding angles are congruent

• Their corresponding sides are proportional

D

G

H

B

C

E

F

AB = BC = CD = AD

GE EF FH GH

L

O

10.5

4

18

M

P

12

12

9

Q

N

Ex. 2: You have been asked to create a poster to advertise a field trip to see the Liberty Bell. You have a 3.5 inch by 5 inch photo that you want to enlarge. You want the enlargement to be 16 inches wide. How long will it be?

X = 22.9 inches

5

The length of the enlargement will be about 23 inches.

3.5

Scale Factor – the ratio of the lengths of two corresponding sides of similar polygons

Ex. 3: a field trip to see the Liberty Bell. You have a 3.5 inch by 5 inch photo that you want to enlarge. You want the enlargement to be 16 inches wide. How long will it be?Parallelogram ABCD is similar to parallelogram GBEF. Find the value of y.

Y = 19.2

Homework a field trip to see the Liberty Bell. You have a 3.5 inch by 5 inch photo that you want to enlarge. You want the enlargement to be 16 inches wide. How long will it be?

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