ratio (redirected from Cross ratio)

ratio. The ratio of two quantities expressed in terms of the same unit is the fraction that has the first quantity as numerator and the second as denominator. For example, if in a group of 100 people 5 die, the ratio of deaths to the total number in the group is 5/100=1/20=.05. Ratios are indicated also by writing the two values with a colon between them, e.g., the ratio of 4 to 8 can be expressed by 4:8 as well as by 4/8.

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ratio

Quotient of two values. The ratio of a to b can be written a:b or as the fraction a/b. In either case, a is the antecedent and b the consequent. Ratios arise whenever comparisons are made. They are usually reduced to lowest terms for simplicity. Thus, a school with 1,000 students and 50 teachers has a student/teacher ratio of 20 to 1. The ratio of the width to the height of a rectangle is called an aspect ratio, an example of which is the golden ratio of classical architecture. When two ratios are set equal to each other, the resulting equation is called a proportion.