Answer
The constant of variation is $0.2$.
The variation equation is $y=0.2\sqrt x$.
Work Step by Step
$y=k\sqrt x$
$y=0.4; x=4$
$0.4=k\sqrt 4$
$0.4=k(2)$
$k=0.2$
$y=0.2\sqrt x$
The constant of variation is $0.2$.
The variation equation is $y=0.2\sqrt x$.
