What Is the Probability of Drawing All White Balls in This Experiment?

[mr_k]

HI, sorry about the english
can you help me with this question?


box initially contains 10 black balls and 10 white balls. The following experiment is repeated indefinitely 20 times : A ball is drawn from the box; if the ball is black it is put back in the box, otherwise it is left out.
what is the probability to draw out all 10 white balls?

i need solve this with combinations.
i know that have (20 k) to draw K white balls and k<=10.hence Sample space :
http://img268.imageshack.us/img268/1744/lllfm.jpg

ו don't know to continue...
thanks!

 

[moonman239]

The answer is the reciprocal of the number of possible combinations.

 

[mr_k]

Hi
i need to find a formula for this.

 

[firavia]

Try to solve your problem using the tree diagram , and add all the probabilites of having 10 blacks ."well the tree diagram is going to be huge". but it works , I know there is another way to do that , but I am not familiar with.

 

[mr_k]

HI
The result is not important i need a formula.