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Ratios and Proportions

The relative values between quantities - ratios and proportions.


The ratio of one quantity to an other is a fraction - and the number of times one quantity is contained in another quantity of the same kind.

The ratio between two quantities is the quotient obtained by dividing the first quantity by the second.

Example - Ratio

The ratio between 3 and 6 can be expressed as

3 / 6 = 1 / 2 = 0.5

Ratio can also be indicated by the sign ":" - like 3 : 6 or 1 : 2 .

Ratio x/y chart

Reciprocal or Inverse Ratio

The reciprocal or inverse ratio is the opposite of the original ratio.

Example the Inverse Ratio

The inverse ratio between 6 and 3 can be expressed as

6 : 3  = 2 : 1 = 2


Proportion is the equality of ratios.

Example - Proportion

1 : 2 = 3 : 6


1 : 2 :: 3 : 6

Related Topics

  • Basics

    Basic engineering data. SI-system, unit converters, physical constants, drawing scales and more.
  • Mathematics

    Mathematical rules and laws - numbers, areas, volumes, exponents, trigonometric functions and more.

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