Geometry Warm-Up1/13/11 1) 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. 2) 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 Polygons are similar when 1) Their corresponding angles are congruent 2) Their corresponding sides are proportional A B C D E F G H ABCD ~ GEFH AB = BC = CD = AD GE EF FH GH

Ex. 1: Decide whether the figures are similar. L M N O P Q

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? Scale Factor – the ratio of the lengths of two corresponding sides of similar polygons X = 22.9 inches The length of the enlargement will be about 23 inches.

Ex. 3: Parallelogram ABCD is similar to parallelogram GBEF. Find the value of y. Y = 19.2

Homework Page 392 (8 – 18 E; 22)