direct proportion
What direct proportion means in Mathematics GCSE, as defined for AQA, Pearson Edexcel.
Definitions of direct proportion
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Reference: AQA
A relationship of the form X = kY for a constant k, so X increases as Y increases and the graph is a straight line through the origin.
A relationship in which one quantity is a fixed multiple of the other, so y = kx and the graph is a straight line through the origin.
One quantity is a constant multiple of another, so y = kx and the graph is a straight line through the origin.
A constant ratio between the two rows of a table points to this, and doubling one quantity doubles the other.
Two quantities increase together at a constant ratio, so y = kx, where k is the constant of proportionality.
This kind of proportion is direct, so doubling one quantity doubles the other.
Topics that use direct 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
- equality of ratios
- inverse proportion
- Multiplier
Using direct proportion in the exam
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