Answer
variation constant $=k=1.8$
Equation of variation: $y=1.8x$
Work Step by Step
$y$ varies directly as $x$ so the variation is direct.
The equation of a direct variation is of the form $y=kx$ where $k$ is the constant of variation.
To find the value of $k$ substitute the given values of $x$ and $y$ into $y=kx$ to obtain:
$$y=kx
\\0.9=k(0.5)
\\\frac{0.9}{0.5}=\frac{k(0.5)}{0.5}
\\1.8=k$$
Thus, the equation of the variation is $y=1.8x$.
