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 Everyday Examples
 Cross-product Property:  For two ratios, if a/b = c/d, then ad = bc.

Image source: http://www.njpsa.org/graphics/catering.jpg

The cross-product property can be used to find unknown amounts in a proportion. For example, the catering business produces food in large quantities. If a recipe that serves 5 requires 2 pounds of beef, then a recipe that serves 180 should require 72 pounds of beef. You can find this answer using the proportion 2/5 = x/180. Using the cross-product property will help you simplify this equation to 360=5x. Then, after dividing both sides by 5, you end up with x = 72.