# Proportionality facts for kids

A **proportionality relationship** happens when two quantities or numbers *x* and *y* are related multiplicatively by a fixed number. This can occur when either their ratio *x*/*y* is a fixed number (direct proportionality), or their product *xy* is a fixed number (inverse proportionality). If *x* is directly proportional to *y*, then we write . The fixed number of a proportionality relationship is called the constant of proportionality.

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Proportionality Facts for Kids. *Kiddle Encyclopedia.*