[/quote]
Eva,
Sorry to open this old thread. But, in this post :
math-combinatorics-87345.html , the poster has mentioned that "Number of ways to pick 0 or more objects from n identical objects = n + 1" -- Hence, the number of ways to pick 2 balls out of say 5 identical balls must NOT be 5C2 -- Correct? Please help me.
thanks[/quote]
The wording
"Number of ways to pick 0 or more objects from n identical objects = n + 1" is not clear.
It is meant that from n identical objects, we can choose none (which is 0), 1, 2,..., or all n objects - therefore we have n+1 choices.
For example, if we have 5 identical balls, we can choose 0, 1, 2, 3, 4, or 5 balls. We have a total of 5 + 1 choices.
Once we made up our mind how many balls we want to choose, say 2, then the number of possibilities to choose them is 5C2 = 5*4/2.
Because, for the first ball 5 possibilities, for the second 4 possibilities, and then we have to divide by 2!, because the balls are identical, order doesn't matter (I would say it is meaningless, red is red, so why should I care which red I picked first?).[/quote]
Hi,
i have a small doubt in this.
This example of 5 balls and pick up 2 ball can be written as like this also right
Probablity to take first ball is : 2/5
Probablity to take second ball: 1/4
so independent event = 2/5* 1/4= 1/10
which is reciprocal of wat u got. . is this correct answer.? i am trying to understand this in probablity ways/ pleas healp me
Thanks,
Rrsnathan