Proportionality (mathematics)

In mathematics, two variables are proportional if a change in one is always accompanied by a change in the other, and if the changes are always related by use of a constant multiplier.

The constant is called the coefficient of proportionality or proportionality constant.

Discussion

If one variable is always the product of the other and a constant, the two are said to be directly proportional. x and y are directly proportional if the ratio \tfrac yx is constant.

If the product of the two variables is always equal to a constant, the two are said to be inversely proportional. x and y are inversely proportional if the product xy is constant.

See also

• Analogy
• Aspect ratio
• Golden ratio
• Mathematics
• Measurement
• Number
• Ratio
• Scalability
• Scale (ratio)
• Scaling (geometry)

External links

• Proportionality (mathematics) @ Wikipedia