Originally Posted by

**305boy** I understand the basics of variations, but am having trouble when numbers are applied. For example, I have the following problem:

"Assume that *y* is directly proportional to *x*. Use the given *x*-value and *y*-value to find a linear model that relates *y* and *x*.

*x* = 9, *y* = 36 "

y is directly proportional to x ... y = kx

**y = 4x** ... would be a linear equation, right?

The same goes for this problem:

"Find a mathematical model representing the statement. (In each case, determine the constant of proportionality.) *y* is inversely proportional to *x*. (*y* = 7 when *x* = 32.)"

y is inversely proportional to x ... $\displaystyle \textcolor{red}{y = \frac{k}{x}}$

$\displaystyle \textcolor{red}{y = \frac{224}{x}}$