This may be the wrong forum, but are there any natural contexts (physics, economics, etc.) in which one might observe the relationship $y = ax/(bx+c)$ between a pair of variables $x$ and $y$? General linear fractional expressions come up all the time in optimization but I've had a hard time finding a really simple and natural context where this might arise. Thanks!
See the MichaelisMenten equation in biochemistry. 

