# Geometry Warm-Up1/13/11 - PowerPoint PPT Presentation

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Geometry Warm-Up1/13/11. 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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Geometry Warm-Up1/13/11

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### Geometry Warm-Up1/13/11

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.

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

### Are the following similar?

Similar – same shape but different size

### Similar Polygons

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

### Ex. 1: Decide whether the figures are similar.

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

Y = 19.2

### Homework

• Page 392 (8 – 18 E; 22)