Tools for Possibilities: issue no. 4

Once a week we’ll send out a page from Cool Tools: A Catalog of Possibilities. The tools might be outdated or obsolete, but the possibilities they inspire are new. Sign up here to get Tools for Possibilities a week early in your inbox.

Math without batteries
Casio FX-115 Solar Calculator, $16
I bought my Casio FX-115 Solar Calculator 25-years ago, probably in Malaysia. It replaced my then aging Texas Instruments calculator. The thing I like most about it is that it doesn’t need batteries. None. You can pull it out of a drawer after a year and it just works. No fretting about whether you left it on or not, and I’ve never needed to replace anything.

The new ones come with a dual solar and battery combo called “solar plus”. Don’t be fooled. The closest new equivalent is probably the Casio FX-260 Solar ($9.99), but that model doesn’t have some of the features of the FX-115.

As far as calculations go, it has pretty much all anyone would need. It has a nice friendly EXP button for scientific notation and infinite levels (18) of parenthesis. It converts and computes in alternate number bases (binary, octal and hex) and does linear regression.

The plastic is a bit scuffed after riding around in my backpack all these years, but it’s been wet and recovered. It also gets really sluggish when used outside in sub zero © weather. – Derrick Oswald

Note: The FX115 comes in two very similar models, the ES and the MS, that feature minor differences. However, it appears that the MS is preferred by some math teachers, and is approved to be used on many licensing exams (where as the ES has in the past not been approved for some engineering exams in California.)
Tried and true number cruncher
HP 10B Business Calculator, $45
HP’s mid-range business calculator has been around for more than 25 years, and it is still the best choice for all but the hardest-core finance, statistical and actuarial uses. For everyday use by business managers doing profit margin, sell/cost, IRR, percentage, mortgage, cash-flow, discount, net present value and so many other common business computations, it offers incredible ease without requiring the user to learn the RPN notation of HP’s higher-end financial calculators.

Everything about the 10B shows an incredible level of attention to design, from the solid rubber feet, perfect tactile keypress response, and easy-to-read, molded-in key labels. And amazingly, my 10B, purchased in 1989, is still going strong on its factory-supplied button batteries, after some 20 years of dependable and regular use.

Loan amortization calculations, even with a computer, can be tedious, but the 10B’s dedicated functions, for all the usual as well as the out-of-the-ordinary loan computations, make such work quick and reliable. As with all functions on the 10B, I simply input the known values using their dedicated keys (for example, number of months, interest rate per year, and loan amount), and then press the key for the unknown value (monthly payment). Change any of the values, and the 10B can re-compute all the remaining figures just as easily.

HP has updated the 10B now to the 10BII, though user reviews on Amazon are not very positive. If you can find a used model on Amazon or eBay, it’s probably the last calculator any businessperson will ever need to buy. – Mike Sullivan
Engineer’s calculator
Texas Instruments TI-89 Titanium Graphing Calculator, $137
I’ve been using a ti89, first the original release and then the titanium release, since I was in high school. It is a calculator for the hardest core of geeks.

Throughout engineering school–I’m working toward my Masters in Mechanical Engineering–I’ve used the programming app to code contours of cam surfaces as well as a host of matrix and kinetics/kinematics programs. It’s a graphing calculator, which allows me to overlay 99 plots of different functions; I can turn on and off different plots to select which functions I’d like to compare.

The ti89 comes standard with a suite of calculus tools such as integration and derivatives, as well as many linear algebra operations. It also comes with support from a Texas Instruments-based free online app store, as well as a programming editor that allows the user to write his own code. There are also preloaded finance and electrical engineering programs.

I own three of these handy calculators: one for my desk at work, another for my desk at home and one for my laptop/school bag. – Benjamin Abruzzo
Advanced calculator on iOS
Quick Graph, iOS
I recently returned to school after a long hiatus. While learning pre-calc and calculus, I found Quick Graph for iOS to be the best graphing calculator. It graphs both 2D and 3D functions. The app also handles multiple functions which are allocated different colors automatically. Unlike stand-alone calculators you can zoom in and out with standard pinch gestures, and in 3D you can rotate the graph in any direction. It also helps that the interface is intuitive: for instance to change the color of your function, there is a little arrow bullet in your current color next to your function in the function list: you just click it and it opens a color selection dialog.

The free version is very functional and has no ads or annoyances. The full version gives extra features such as unlimited functions (free is limited to 6) and tracing the graph by tap and hold (it is easy estimate the same data in the free version, but it won’t give you the exact value).

Unfortunately, my iPhone broke and I am now using Android on which I have not found a graphing app of the same level of intuitive design. – Aryeh Abramovitz

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