Street-Fighting Mathematics
The first rule of street-fighting mathematics is…

The first rule of fight club is you do not talk about fight club
Math is always portrayed as exacting and calculating, but there is a great need for those that deal with numbers on a regular basis to also have a sense for approximate answers. Throughout engineering school it is often referred to as “back of the envelope” calculation. Quick and dirty approximation that gives a sense of the exact answer.
A colleague pointed me to a class called “Street-Fighting Mathematics” over on the MIT Open Course Ware site. MIT OCW is a site with lecture notes, readings, exams and videos from quite a few classes. Now you have no excuse for sitting around doing nothing on a Friday night! Street-fighting Mathematics is taught by Sanjoy Mahajan, and it looks pretty well put together.
The course description reads:
This course teaches the art of guessing results and solving problems without doing a proof or an exact calculation. Techniques include extreme-cases reasoning, dimensional analysis, successive approximation, discretization, generalization, and pictorial analysis. Applications include mental calculation, solid geometry, musical intervals, logarithms, integration, infinite series, solitaire, and differential equations. (No epsilons or deltas are harmed by taking this course.)
Seems to be the thing everybody should review every once in a while. Here is your first assignment, now get to work!

