Almost-great scientific calculator for real world math.

I originally bought a TI-30X IIS for about $16 at Office Depot. I liked the unit, and gave it a 5 star review here at epinions. Then I lost it, but since they’re not expensive, I went out and bought another one. Strangely, my new TI-30X IIS is not identical to the first one I had, and the differences are not for the better, which made me lower my opinion to 4 stars. But I’ll get to that later... If you’ve been making do with those ubiquitous 4-banger ‘cheapie’ calculators, you’ll really like the TI-30X IIS.

By far the best feature of this calculator is the 2-line display, which shows your equation on the top line and the answer on the bottom line. This lets you type in a long formula (up to 88 characters) and then use arrow keys to go back and make corrections without having to retype the whole thing. For example, if you type 10 * 20 * 35 * 40 * = and you meant to type a 30 instead of the 35, you just hit up arrow, and a bunch of right arrows until you get to the '5', and type in a '0' right on top of it. Then just hit enter and the equation will re-compute. This feature alone is worth the price of the unit IMO.

There are two features of this calculator, which, individually are useful, and when used together, give you quite a surprising amount of computing power.

The first is the ‘Constant’ feature (labeled ‘K’). Constant lets you write a formula to memory. You can then apply the formula to any value with the = key. For example, the formula to convert from Celsius to Fahrenheit is x * 9 / 5 + 32. If you had to convert a page full of Celsius temperatures, you would just type in that formula, store it as the Constant, and then enter the Celsius values you want to convert like this:

15 =
59

0 =
32

-40 =
-40

etc.

The second feature is that you can set 5 different numbers in memory. This is very handy when you need to find several solutions and then use those solutions with each other to find a new answer. If you don’t know how to use memory values, then I advise you skip to the end of this review because this next section won’t make sense to you.

Still with me? Good, because now comes the cool part… using Constant and multiple memory values together.

Suppose you had to solve a page full of quadratic equations. You remember those, right? Quadratics are equations of the type:

ax^2 + bx + c = 0

Sounds like a lot of work, eh? Well, NOT SO if you have your TI-30X IIS handy. Simply enter the quadratic formula into Constant, load your a, b and c values into your first three memories, and, viola, you’re done.

So consider this quadratic:

3x^2 + 4x + (-39) = 0

How would you solve for x?

It’s a cinch! Enter the quadratic formula into Constant like this:

K = (-b + square-root-key ((-b)^2 – 4 * a * c)) / (2 * a)

Then load your a, b and c values like this:

A = 3
B = 4
C = -39

Then press = and you get:

=
3

Now all you have to do is change the a, b and c values as you work your way through your page full of quadratics. When you finish, you can go back and modify the quadratic formula to be:

K = (-b - square-root-key ((-b)^2 – 4 * a * c)) / (2 * a)

And start from the top again to get all the second solutions. How cool is THAT? By using Constant and multiple memories together, you can do all the algebra and trig you’re likely to run into.

On the down side, an annoying limit of the calculator is that it will not let you set memory values by using the form C= A + B.

Other points:

The TI-30X IIS can handle fractions (fraction mode takes a bit of getting used to, but once you get the hang of it, it works well).

It has probability functions (for proving to your friends that Lotto is actually a tax on people who are bad at math!)

It has statistical functions and can find mean, standard deviation etc., but then, it’s tedious hand-entering data.

It can operate in 3 different angle modes (degrees, radians, and grads).

Where the TI-30X IIS loses points with me is in its construction. As I mentioned at the beginning of this review, the replacement I bought was different from the original one I had. While my first one was made of black plastic and seemed solid… with a poorly designed (though tightly-snapping cover), my new one has a bluish caste to it and the cover slips about 1/4 inch whether its attached to the front of back. Also, if you press even a little on the display screen (like when you’re wiping off dust) you get LED smear. And speaking of dust, dust collects under the screen, and I can’t think of a way to clean it out of there.

As other people have mentioned, there are no little rubber feet on the back, so you can’t just put it on your desk and use it with one hand because it slides around. The keys are spongy and don’t ’click’. The calculator is not capable of RPN, nor can you graph or transfer data, though really, what do you expect for 16 bucks?...

The TI-30X IIS is both portable and 'legal' for math students to use on exams, but IMO, ALL calculators are far inferior to a computer running decent math software (such as Excel, MathCAD, Maple, or Mathematica). For anything more than casual math, you will be much happier using a computer. Personally, I do about 80% of my math in Excel, and the other (most complicated) 20% in MathCAD. While I routinely exceed the capabilities of my TI-30X IIS, I've never yet encountered a problem which couldn't be handled with one of the above-mentioned softwares.

When the price of Pocket PC’s comes down a little more, I’ll buy one so I can run Pocket Excel, and I’ll give this TI-30X IIS to my kid. But in the mean time, for 16 bucks, despite me dropping my rating from 5 to 4 stars, I still consider it a good buy and a handy tool.