Why the number of ways of selecting $r$ things out of $n$ identical things is 1 Would some one please provide me a detailed information regarding -
"why the number of ways selecting $r$ things out of $n$ identical things is 1".
Here is my example - let's say I entered into clothes shop and I saw a set of 100 identical shirts. So if I have to select any 5 out of these 100, I can select them in 
even series or odd series or multiples of 10 series or first 5 or last 5 or randomly any 5 right? then why every where I am seeing just "1" as answer.
 A: If you have five objects $A,B,C,D$ and $E$, then the number of ways of choosing $r,1\le r\le 5$ objects out of these five is $n \choose r$. But if the five are identical and are $A,A,A,A$ and $A$, then there is no "way" to choose. If you need 2 objects, the choice is AA; if you need three, the choice is AAA and so on. 
So there is just "one way" or one choice when the objects are identical.
A: That is because however you chose, since they are all identical, you can not precisely say that the one you have was not the one you didn't chose from the given sample.
Consider it like this:
You have 3 trucks full of sand and you want to select 5 kg from it. Now, it doesn't matter how many times you take it out, how much quantity you take out with each turn as long as you, at the end, have just 5 kg of sand with you.
On the other hand, if I'm to have other constrains on the same example, such as first truck can not provide more than 1 kg, you must take at least 3 kg from 2nd and so on, the calculations would change.
Similarly, in your example, you're constraining your selection based on their positions in the shop. While, no such thing is mentioned in the original question.
A: The shirts are identical, meaning that no matter if you selected shirts number 1,2,3,4,5 or 5,10,15,20,25, the result will be the same: You have 5 idendical shirts and the shop has 95 identical shirts.
