advertisement

Ratios and proportions Definitions • Ratio: is a comparison of two numbers by division. • Example: x to y; x:y; x/y or x divided by y • Means-Extremes Property of Proportions: In a proportion, the product of extremes is equal to the product of the means. Example: if a/b =c/d, then ad=bc Definitions • Scale: is a ratio used when making a model to represent something that is too large or too small to conveniently be drawn at actual size. Example • 3/6 = x/2, here x = 1. Cross multiply to get the answer, so 3*2 = 6*x, which is • 6 = 6*x, divide both sides by 6 and • X=1 Solve • 4/7 = n/14 • Answer, n = 2 • 12/20 = r/45 • Answer, r = 2 • Is the following a true proportion? • 36/45 = 32/40 • Answer 1440 = 1440, so yes.