Relationship between real numbers, such that, for all real numbers x and y, there exists a real number r such that [latex]\dfrac{x}{y}=r[/latex].
Examples
A relationship of proportionality defines a linear function of the form f(x) = mx, where the parameter m (called the slope of the graph of f) is the coefficient of proportionality.
Consider the following sequences 1 and 2 :
Sequence 1 : 2 5 8 11 14 17 20
Sequence 2 : 6 15 24 33 42 51 60
Each term in sequence 1 is multiplied by 3 to obtain each term in sequence 2.
Therefore, the relationship of proportionality between the sequences 1 and 2 is : [latex]r=dfrac{1}{3}[/latex].
