Key Stage 4
About Direct Proportionality
- A scatter graph showing a directly proportional relationship has line with a linear gradient that passes through zero (it has a y-intercept of zero).
- On a proportional scatter graph when one variable doubles, the other doubles or when one triples the other triples.
- When two variables are directly proportional when any value for y is divided by its corresponding value for x it will always give a constant value.
- Two variables are said to be directly proportional when they always vary by the same ratio.
- Straight line [1 mark]
- Passing through zero / passing through the origin [1 mark]
|This scatter graph shows a linear relationship that is directly proportional where x doubles, y doubles.
\(y = mx\)
Where m, the gradient, is positive.
- Directly proportional, pages 158-159, 282, GCSE Physics; Third Edition, Oxford University Press, AQA