Basic Math: When will I use that?!
The last two days I’ve used two basic math equations for a practical purpose — so all you middle schoolers out there, this stuff does eventually come in handy. Really.
The first was the pythagorean theorem — remember a2+b2=c2? Well, I bought a projector screen on Ebay and wanted to know how wide it was to plan for mounting. I know the aspect ratio is 16:9 and the diagonal is 105″. The math:
(16x)2 + (9x)2=1052
256x2+81x2=11,025
337x2=11,025
x2= 32.715…
x=sqrt(32.715…)
x=5.72
16x = 91.5″ or a bit over 7-1/2 feet wide, assuming I didn’t screw any of that up
Today Lizz was listing rings on Ebay for sale but didn’t know their size. She was having trouble with the direct “ribbon” method of measurement (wrapping a ribbon inside the ring, then measuring), so instead she measured the diameter of the ring. I (a bit shamefully) had to Google up the equation to calculate the circumference of a circle from the radius, which is 2*r*pi. Since the diameter is just twice the radius, simply multiply the diameter by pi (3.14) and look up the result on a ring size chart.
Next up, differential calculus around the house…
May 8th, 2006 at 7:09 pm
I find myself doing a lot of basic math of the Fermi problem variety. Instead of how many “piano tuners are there in Chicago?” most recently it was “how many cars are there in downtown Chicago during the business day and how does it compare to the emissions from outdoor smoking?” A good bullshit detector should always include some “order of magnitude” type calculators.
The other place where I find basic mathematical reasoning at work on a daily basis is looking at graphs. First question, always: does the graph’s dimensionality sanely correspond to the dimensionality of the underlying phenomena. The NY Times, usually pretty good about these things, recently ran an illustration of big 3-dimensional W filled with “water” to compare… Bush’s economic approval rating to his overall poll rating. 3 dimensions and a lot of column inches for two one dimensional datapoints. Ahem?
May 8th, 2006 at 7:17 pm
Edward Tufte would be rolling in his grave, but he’s not dead.
And if you’re wondering what I’m talking about, read this book. The title is boring and it has a somewhat baroque appearance but hot DAMN it’s a good book on reading and designing well, visual display of quantitative information.
May 9th, 2006 at 9:55 am
I went to one of his conferences. Highly recommended — completely worth the money. If you’re a student, it’s the price of buying all his books, but … you get copies of all his books.
Neatest thing he used for show-and-tell: an excellent condition book from the 17th century that did 3 dimensional geometrical proofs with little tabs of paper that folded up to actually make cubes, pyramids, etc.