PRACTICAL GUIDE · UTILIA WORK

Direct and inverse proportions: explanation and examples

Use proportional relationships to find an unknown value.

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The calculation

For a direct relationship, if A corresponds to B, then C corresponds to X = B × C ÷ A. For an inverse relationship, X = A × B ÷ C.

Worked examples

Direct: if three notebooks cost €12, five cost €20. Inverse: if three people take twelve hours, six would take six hours, assuming identical productivity.

Check the assumption

First establish that the relationship is truly proportional. Not every everyday problem can be solved this way.

General educational information. Examples are illustrative; check the conditions and rules applicable to your situation before making important decisions.

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