# ratio

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## 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.

## Ratio

A relationship in magnitude, quantity, or degree between two or more similar things.

## 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.

## ratio

[′rā·shō]
(mathematics)
A ratio of two quantities or mathematical objects A and B is their quotient or fraction A / B.

## ratio

Maths a quotient of two numbers or quantities
References in periodicals archive ?
The posteroanterior chest radiograph demonstrates slight pulmonary plethora, a large pulmonary trunk and proximal pulmonary arteries, and a cardiothoracic ratio of 0.
A fetal echocardiographic screening examination involves visualization of a four-chambered view of the heart with the atrial and ventricular septum and right and left ventricular outflow tracts, as well as measurements of ventricular length, cardiothoracic ratio, and other cardiac dimensions.
Her chest-X ray revealed an increased cardiothoracic ratio and 12-lead ECG showed low voltage with a heart rate of 100 beat/min.

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