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:            


                                                            Try two practice problems:


                                                                                    Do the following:



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


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







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