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.

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ratio

Maths a quotient of two numbers or quantities

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ratio [′rā·shō]

(mathematics)

A ratio of two quantities or mathematical objectsAandBis their quotient or fractionA/B.

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Ratio 

The ratio of two numbers is the quotient from the division of the first number, by the second. The ratio of two homogeneous magnitudes is the number obtained by measuring the first magnitude when the second is chosen as the unit of measurement. If two magnitudes are measured in the same unit of measurement, their ratio is equal to that of the numbers that measure them.

The ratio of the lengths of two segments may be expressed by a rational or irrational number. In the former case the segments are said to be commensurable, and in the latter incommensurable. Mathematicians of the ancient world had no knowledge of irrational numbers. For them the concept of the ratio of two segments did not reduce to the concept of number. In their conception the geometrical theory of the ratios of magnitudes was not connected with the concept of number and played an independent role. In a sense, it substituted for a theory of real numbers. Indeed, according to Euclid the four segments, a, b, a’, and b’ form the proportion a: b = a’:b’ if for any natural numbers m and n one of the relations ma = nb, ma > nb, ma < nb is satisfied simultaneously with the corresponding relation ma’ = nb’, ma’> nb’, or ma’ < nb’. It follows that when a and b are incommensurable the subdivision of the rational numbers (x = m/n) into two classes according to whether a > xb or a < xb coincides with the subdivision according to whether a’ > xb’ or a’ < xb’ —this is the idea behind the modern theory of Dedekind cuts.