In a direct variation, one quantity is directly proportional to the other, i.e as one quantity increases, the other increases too and vice versa;
This can be expressed mathematically as;
[tex]y\text{ }\alpha\text{ x}[/tex]The eliminate the sign of proportionality, we introduce a constant as shown;
[tex]y=kx[/tex]So if we compare the given equation y= 2.5x to the above equation, we can deduce that k, which is the constant of proportionality, is 2.5
