inverse proportion
What inverse proportion means in Mathematics GCSE, as defined for AQA, Pearson Edexcel.
Definitions of inverse proportion
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Reference: Pearson Edexcel
A relationship in which the product of the two quantities stays fixed, so y = k/x, and with k positive the graph is a curve that falls as x grows for positive values of x.
A relationship where X is proportional to 1/Y, written X = k/Y, so as Y increases X decreases and the product XY stays constant at k.
One quantity decreases as the other increases so their product stays fixed, giving y = k ÷ x, often written y = k/x.
Saying X is inversely proportional to Y is the same as saying X is proportional to 1/Y, the reciprocal of Y.
X is inversely proportional to Y is equivalent to X is proportional to 1/Y, so X = k/Y, equivalently XY = k.
The product is constant, so y = k/x and the graph is a curve that never touches the axes.
Topics that use inverse proportion
- Ratio, proportion and rates of change (AQA GCSE)
- Ratio, proportion and rates of change (Pearson Edexcel GCSE)
Related terms
- compound interest
- Compound Measure
- compound unit
- constant of proportionality
- Density
- direct proportion
- equality of ratios
- Multiplier
Using inverse proportion in the exam
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