Math

Here is what in the comments of one of Mankiw's post:

Mathematical Equations and the Real World

* Engineers think that equations approximate the real world.

* Scientists think that the real world approximates equations.

* Mathematicians are unable to make the connection....

I will add one more:

* Business folks think equations are exactly the same as real world: $1 = $1, $2 = $2, $3 = $3 ......