likewise here, we do the same, pick any of the points, say (10, 5).
[tex]\bf \qquad \qquad \textit{direct proportional variation} \\\\ \textit{\underline{y} varies directly with \underline{x}}\qquad \qquad y=kx\impliedby \begin{array}{llll} k=constant\ of\\ \qquad variation \end{array} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \begin{cases} x=10\\ y=5 \end{cases}\implies 5=10k\implies \cfrac{5}{10}=k\implies \cfrac{1}{2}=k[/tex]
If we assume your equation is ...
... y = k/x . . . . . . the equation of inverse variation
the value of k is found from any ordered pair of values.
... x·y = k . . . . . . multiply the above equation by x
... 4×12.5 = 5×10 = 10×5 = 20×2.5 = k = 50
The constant in the above equation is 50.
