What I Learned: Point-slope formula

Probably the biggest thing college did for me was in the area of math refresher. Ashamed to say I had let my math skills slip mightily over the years.

I know I probably learned this formula in high school but since there was a 30-year gap for me between high school and college, I guess I plumb forgot it!

The point-slope formula (also known as the slope-intercept equation) was the very first thing I learned in remedial math class. Those of us who failed the math assessment during student orientation had to take this extra class designed to get us up to speed before taking real college math.

First day of class Dr. Jessica Knapp (who looks nothing like a math teacher, by the way!) brought stacks and stacks of styrofoam cups and passed out maybe 10 or 12 cups to each group of 2 or 3 students. Our task was to construct a formula that would tell her how high the stack was. And the formula had to work even when she combined two of the stacks.

Some of the students got out their trusty ruler, measured one of the cups, and multiplied that by the number of cups. Okay, okay, I almost did the same thing. But then I noticed another measurement we needed to have. The distance between the lip of the first cup and the lip of the second.

So you really need TWO measurements in this formula. One will be used just once, and the other will be repeated as many times as you have cups. This is called the point-slope formula: y = mx + b

y is the height of the entire stack
m is the number of cups
x is the height of the lip
b is the height of the first cup below the lip

So the height of the stack is 12 (cups) x .5 (half an inch) + 4 (inches)

I can’t tell you how many times over the course of my four year college career this formula popped up. Over and over and over again - in economics, finance, statistics - everywhere. Very useful formula! I think it's magic in its simplicity.