Ratio, proportion & rates of change · Direct & inverse proportion
Chapter 1 · 3
The idea
Inverse proportion
Why "inversely proportional" means the product stays fixed, how worker-time problems really work, and how to tell inverse proportion apart from direct.
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Ratio, proportion & rates of change · Direct & inverse proportion
Inverse proportion
Why "inversely proportional" means the product stays fixed, how worker-time problems really work, and how to tell inverse proportion apart from direct.
Why it works
The product never changes
Two quantities are inversely proportional when one goes up by the same factor the other goes down by: double one and the other halves, triple one and the other drops to a third. In symbols, meansThe second form is the useful secret: in inverse proportion the product of the two quantities never changes. That fixed product is the "total amount of stuff" in the problem — and once you have it, every other pair of values is one division away.
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The rest of the explanation, plus 2 worked examples you step through move by move.
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