7.3. Similar Polygons and Scale Factors http://www.ck12.org
Example C
ABCD∼AMNP. Find the scale factor and the length ofBC.
Line up the corresponding sides,ABandAM=CD, so the scale factor is^3045 =^23 or^32. BecauseBCis in the bigger
rectangle, we will multiply 40 by^32 because^32 is greater than 1.BC=^32 ( 40 ) =60.
Watch this video for help with the Examples above.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52543CK-12 Foundation: Chapter7SimilarPolygonsandScaleFactorsB
Concept Problem Revisited
All of the sides in the baseball diamond are 90 feet long and 60 feet long in the softball diamond. This means all the
sides are in a^9060 =^32 ratio. All the angles in a square are congruent, all the angles in both diamonds are congruent.
The two squares are similar and the scale factor is^32.
Vocabulary
Similar polygonsare two polygons with the same shape, but not necessarily the same size. The corresponding
angles of similar polygons arecongruent(exactly the same) and the corresponding sides areproportional(in the
same ratio). In similar polygons, the ratio of one side of a polygon to the corresponding side of the other is called
thescale factor.
Guided Practice
1.ABCDandUV W Xare below. Are these two rectangles similar?