A rectangle has an area of 36 square units.As the length and the width change,what do you know about their product? Is the length proportional to the width?

I'm assuming that the 36 square units is the constant  area.  If so...the product of the length times the width  is constant........note that

Each side could be 6 units

Or......one side could be 9 units and the other 4  units.

But

L / W =  6 /6  isn't proportional to L /W =  4 / 9