Online tool to check if number is rational or irrational?

I am new to this forum. I've been programing for some time, and now starting my engineering degree. I am trying to find an online utility that will help me grasp the concept of irrational numbers (summary, multiplication, devision etc.) through trial and error. I am looking for an online tool that will give me a yes no answer if a number is rational or irrational (I will keep my numbers low).

Do you know of any such tools? I Hope this question is in the right stackexchange site.

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migrated from mathematica.stackexchange.comAug 27 '12 at 8:24

This question came from our site for users of Mathematica.

Although you've gotten an answer, this is not the right place for this question. Just fyi. – R.M Aug 27 '12 at 6:46
What format do you have those numbers in? Any irrational number will have an infinite, non-periodic decimal expansion, so there is no obvious way to store it on a computer (and no real advantage to "small" numbers). – Tobias Kildetoft Aug 27 '12 at 8:26
Any number you can type in by entering a finite number of digits is always going to be rational. I guess you mean you want to enter expressions like $\sqrt{7}$, $\pi/5$, and so on, and see if they are rational. But this is a surprisingly hard problem in general: for example, nobody knows whether $\pi + e$ is rational or irrational. – Rahul Aug 27 '12 at 8:39
@RahulNarain: That would be good as an answer. – Henning Makholm Aug 27 '12 at 15:24
But @Henning, I don't know if it answers the question. The question asks about numbers, I was only extrapolating about arbitrary expressions. – Rahul Aug 27 '12 at 17:29