Math Is Fun Forum

juantheron

Member

Registered: 2011-10-19

Posts: 312

permutation

The number of ways of forming an arrangement of 4 letters from the letters of the word “IITJEE”

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: permutation

Hi;

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

juantheron

Member

Registered: 2011-10-19

Posts: 312

Re: permutation

Thanks bobbym

Would you like to explain me how can i take

and

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: permutation

Hi juantheron;

A long time ago Abraham DeMoivre came up with the idea of a generating function. This was expanded on by Euler. The idea in is simplest form is that many enumeration problems can be solved by simple polynomial arithmetic. You just have to set them up right. This too is simple but requires a little practice.

Look at the letters i i e e t j

The t and the j can occur once or not at all. They are modelled by the exponential gf:

since there are two of them they are squared.

Now look at the letters i and e. They can each occur 0,1 or two times. They are modelled like this:

because there is two them they are squared.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

juantheron

Member

Registered: 2011-10-19

Posts: 312

Re: permutation

Thanks Bobbym Got it

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: permutation

Hi;

Your welcome, glad to help.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.