A. Definitions

ratio – two quantities measured in the same unit (a fraction)

proportion – an equation with two ratios set equal to each other
 Extremes: "a" and "d"
 Means: "b" and "c"
B. Facts about Ratios and Proportions
 If two ratios are equal, then their reciprocals are equal.
 Example: If then
 To solve a proportion, crossmultiply OR the product of the extremes is equal to the product of the means.
 Example: If , then ad = bc.
 If an "x^{2}" term is obtained after crossmultiplying, solve by factoring or using the quadratic formula.


