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Forum URL: http://www.cut-the-knot.org/cgi-bin/dcforum/forumctk.cgi
Forum Name: College math
Topic ID: 730
#0, infinite probability
Posted by girl_honey on May-22-10 at 06:48 PM
hi i am having trouble with the following question, wondering if someone can help me, thanks in advance

Q. if i have a very large number of pool balls in a bag in the ratio of 3 red to 2 yellow, what is the probability of drawing exactly 2 red and 1 yellow ball from the bag? the number of balls may be considered infinite

thank you.
Oyinkan


#1, RE: infinite probability
Posted by alexb on May-22-10 at 06:54 PM
In response to message #0
Probability of drawing a red ball is 3/5. Do you know why? What is the probability of drawing a yellow ball?

There are three ways to retrieve 2 red and 1 yellow ball. In order of the balls appearance out of the bag:

r-r-y, r-y-r, y-r-r

Probability you are looking for is the sum of the probabilitles of these three events.

The probability of each of these is the product of probabilities of drawing a ball of a given color.


#2, RE: infinite probability
Posted by girl_honey on May-22-10 at 10:12 PM
In response to message #1
thanks for the help. it was the 'infinite' part that confused me

.Oyinkan.