Linear relations > Directly proportional
1234Directly proportional

Theory

You would call a variable y directly proportional to a variable x when doubling x leads to doubling y as well.
The corresponding formula would look like: y = a x .
The graph of a directly proportional relation is a straight line through the origin: ( 0 , 0 ) .

  • a = 25 4 = 6 . 25 is called the constant of proportionality.

  • a determines the steepness of the straight line and is called the gradient of this straight line.

On the right you can see how a determines the steepness of the graph.

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