Question

Variable y varies directly with variable x, and y = 9 when x = 5.

What is the constant of variation in decimal form?

Answer 1

Direct variation:

$\sf~y=kx$

Plug in what we know:

$\sf~9=k(5)$

$\sf~9=5k$

Divide 5 to both sides:

$\sf~k=\boxed{\sf1.8}$

So the constant of variation is 1.8.