Casio FX-991ES scientific calculator with 403 functions and natural textbook...

I use this calculator for teaching on engineering maths on HNC/D and Foundation Degree courses and specify it as the course calculator. It comes into its own for complex numbers, equation solving and tables. It works with matrices but not inverse. It does powers of complex nos up to 4 but not roots. At around £13 its a great deal! There is a set of written examples of how to use various functions which can be useful.

I bought this at the beginning of last year and have used it in all my AS level examinations to great reward. With the integration, series, matrices, vectors and complex number functions, it is extremely helpful in A-level studies and examinations for checking your answers.

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IF YOU'RE BUYING FOR YOUR CHILD: I heartily recommend this calculator to A Level Maths students and beyond. It is THE BEST calculator that is allowed in exams. It will make a grade's worth of difference against similar calculators if you know how to check your answers with these things. It won't tell you what the right answer is for you, but it will tell you if you've got the answer right if you know how to use it. Make them check their answers with it, and hope that they toy around with it and figure out every function. It seriously will get them an extra 10%.

If your child does GCSEs or less, this calculator is pretty nice, especially if you're going to use it later. It won't HURT to have it, but you could equally get a Casio FX 85ES and it wouldn't make a difference.

That's all you as a parent need to really know. If you want this calculator for yourself, feel free to continue.
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So I lost my Casio FX-991ES. I'd been using that since A Level Further Maths (For calculus, complex/imaginary numbers, statistics, vectors, matrices etc.). The solar panel had stopped charging particularly efficiently anyhow so I had had to replace the battery.

Regardless, I then decided since I have exams coming up I ought to get a new one. These things are passable in all exams, because they're not graphical and they don't do definite integration.

The product that came was an FX-991ES PLUS. Looks a little less professional than the FX-991ES but it includes the RanInt function, where you can choose two numbers RanInt(X,Y), and it will randomly generate integer N, where X<=N<=Y.

Also comes with a brand new error, "Argument ERROR" when Y<=X in this case. Yes, I like collecting error messages on my calculator. It's what I do when I'm bored in lectures, alright?

It's thanks to the 991ES that I got into Manchester University. When I was sitting my Core 4 exam I needed >=97% to get an A* in Maths. Although it only does indefinite integration, that's good enough for checking your answers. Pick two random variables for the limits and see if they match your answer, if not divide one by the other and see what factor you're out. In my case it was 3.1415926 so I knew I dropped a pi in a volume of integration somewhere, and got 100%. Woot.

Anyway, then there's the matrix function so you can check your 3x3 matrix inversion is correct, because anyone who's done it knows that's a little b**** to do. You can use the vector formula to make sure your dot products and whatnot are right if you're a noob. You can plug complex numbers into it and find the modulus and argument, which is always convenient for drawing argand diagrams. You can stick stats in a massive table and calculate the standard deviation. You can convert things decimal to hexadecimal, octal and binary (So you can see that 25 DEC is the same as 31 OCT. Admit it, your mind = blown if you understood that).

For probability it does factorials(!), "choosing" and permutations. Only yesterday I was trying to work out, calculatorless (new word), the probability distribution of gene matches with my sibling, to determine whether I should care about his gene pool in light of the birth of his new son yesterday. I think it was Gaussian, but I guess I won't know until I fire up my nCr button.

It does summations too, which is always handy when you're working out binomial expansions. I had to actually REMEMBER the formula for that when my friend and I were working out how many presents in all the singer received during the 12 Days of Christmas. (The answer is 364, as for he receives (13-n)n of each gift where n takes every value between 1 and 12). See, using the summation function on my calculator I just had to type 13X-X^2, X=0, 12 into it and it gave it instantly. Try remembering that 13n becomes 13(n^2+n)/2 and n^2 becomes n(n+1)(2n+1)/6 off the top of your head. Good luck.

It has the INS function, for that 1 time in the history of ever where you derp'd and forgot to put a fraction in. No more pressing AC (or ON. I press ON. Got a problem?) to wipe your display because it'll take too long to rectify it. Simply use shift+DEL to drop that fraction in.

It does probability distributions too if you're doing the stuff of nightmares: Statistics 2. No more readings values off a table; what is this, the 70s? Go into STAT mode, then press AC (not ON, sadly), then SHIFT+1 to bring up and press 5 (Distr). If Z has a normal distribution with mean 0 and variance 1 then for each value of n, the function P(z) gives the probability that Z is less than or equal to n. R(z) is just 1-P(z) and Q=P(z)-P(0). Might help to look at a Gaussian distribution for help with that. There's a nice little picture in the manual..

...

...

.. I would imagine.

(Ahem).

It converts stuff to degrees if you know how compass bearings work. I don't, because I'm neither a navigator, nor a scout leader. It also converts Polar to Cartesian and vice versa (using the Pol and Rec functions. Yeah, I know; these rookies, "Rectangular"...).

And oh, I just realised! if you press right at the end of a line or left at the start this model skips to the opposite side. Now that, my friends, is a welcome change.

The solar panel is protected, but if it isn't so covered in dust that the solar panel doesn't function by the end of the year, I'll give you my vacuum cleaner. It's not like I'm gonna need one in that case.

It already has hair on it. I don't want to put my finger on it though; that's a recipe for disaster. But if you brush it to the side it gets acught in the little dip. Tssk.

It also solves equations for you, and converts degrees to radians and vice versa like a BOSS.

It has 9 STORAGE BUTTONS! 9! No more typing out the values of c and 1/(4*pi*epsilon_0). I wouldn't recommend putting numbers you'll actually need on the X, Y and M buttons, because it's easy to overwrite them by accident by hitting M+ by mistake or using a stat table. I use X and Y for question specific variables, say I'm obsessively storing a number to 9 significant figures. Not to mention the fact that it stores 40 constants and converts 40 types of unit. (Come on, Casio. 40 for both? You just wanted a nice array to stick on your calculator back. There aren't exactly 40 useful conversions and constants; don't lie).

Last, but not least, it provides hours of time killing during maths lessons. Thought you were a badman because you could spell 3 words on your upside down calculator? Try full way up:

A-F = ALPHA keys on the fourth row.
g = DRG 3
H = Abs -
Turn on complex mode for i
J = Square root
K = 1 (
L = 1
M = the M ALPHA button
N = pi
O = 0
P = nPr
Q = 0 ,
R = DRG 2
S = 5
T = CONST 38
U = CONST 17
V = ( )
W = ( ) ( )
X = the X ALPHA button
Y = the Y ALPHA button
Z = 7 or CONST 37. Oh come on, who uses Z?

So some of them aren't that elegant. You're not going to care when you're INCONSPICUOUSLY WRITING MESSAGES TO EACH OTHER DURING CLASS. Best part: You can instantly delete what the other person's written. No more destroying trees every time you want to pass a note. After a few years of doing this you can do it blindfolded at almost writing speed. Yeah. Just that cool. Extra points for craftiness if you type in tricky formulae before an exam, write them on the back of your paper then wipe the screen. It doesn't STORE the writing so it's exam legal. Not that I would ever condone doing such a thing.

Also, when you've finished an exam and you're bored, since you already checked your answers with your calculator, try building a monastry out of fractions and Abs, like:
___+___
_|8||8||8|_
111101111

Those 1s at the bottom should be |s but Amazon messes up the unicode. It's written properly here: http://pastebin.com/aEVqVG90 , but that'll disappear in a month, and I doubt anyone'll read my review within that month. Sadface :( .

It's the perfect calculator for figuring out whether you've answered the question right and reverse engineering methods. Say you forgot how to do the modulus and argument of a complex number in an exam, but need to actually know what they mean? Run those functions with easy test numbers like 3 and 4 and you'll figure out what they mean.

So, as a second year student of Physics with approaching exams that he really should start working for instead of writing an overly detailed amazon review of a calculator, I heartily recommend this for anyone who wants to pass exams. It looks a bit too round, but you'll learn to love it and its "NATURAL-V.P.A.M". Whatever that is.

Oh. Visually Perfect Algebraic Method. Like I was gonna know that from the acronym. Nice assumption, Casio.

Also, these calculators help you in Chemistry, when you need to remember the chemical formula Ca2SiO4. You can thank me later, A Level Chemistry students. You and your fake subject.

Buy it.