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Chapter Seven

Proportions and Similarity

ratio a comparison of two quantities using division.
Extended ratios can be used to compare three or more quantities, example a:b:c
proportion an equation stating that two ratios are equal
extremes In the proportion a/b=c/d, a and d are the extremes
means In the proportion a/b=c/d, b and c are the means
cross products the product of the extremes ad and the product of the means bc are the cross products
Cross Products Property In a proportion, the product of the extremes equals the product of the means.
Equivalent Proportions a/b=c/d, b/a=d/c, a/c=b/d, c/a=d/b
Similar Polygons Two polygons are similar IFF their corresponding angles are congruent and corresponding side lengths are proportional. Their shape is the same, but not necessarily their size.
Similarity Ratio The scale factor between two similar polygons
Scale Factor the ratio of the lengths of corresponding sides of two similar polygons. It depends upon the order of comparison.
Created by: amgeometry