Similar Polygons- Ratio of Perimeter and Area

                                    Lesson 1

 

                                                            Problem:     Two ∆ are similar. The sides of the first ∆ are 21, 13, and 14.

                                                                                  The largest side of the second ∆ is 78. Find the perimeter of the second ∆.

 

                                                            Solution      The ratio of the largest sides of the triangles 13:78 or 1:6

                                                            Step 1:      

                           

                                                            Solution      The perimeter of the smaller triangle is 48

                                                            Step 2:          

                            

                                                            Solution       Set up a proportion 1:6 = 48: x

                                                            Step 3:                                                 x = 288                                           

                   

                                                            Solution        Answer: 288

                                                            Step 4:            

                                    Complete

                                                            Try two practice problems:

                                                                       

                                                                                    Do the following:

 

A.

Two polygons are similar. If the ratio of the perimeters is 7:17, find the ratio of the corresponding sides.

B.

The ratio of the perimeters of two similar triangles is 11:12.  Find the ratio of the areas.

 

 

 

 

 

 

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