bradloff
May 27, 2009, 08:13 PM
Hi all, I am trying to help my daughter with some probability homework. Unfortunately, I'm a bit rusty on these probability formulas, and I have limited notes/books to look at, as the teacher is not taking this from my daughters math book, and my daughters notes aren't too good! :confused:
Anyway, we are trying to calculate the probability of an event after an a previous event has already happened.
One example could be something like this:
There are 10 marbles, 2 white, 5 black, and 3 gray
Question, what is the probability of drawing a white marble from a bag if all marbles are put in the bag at the start? Ok, this one is easy, it is 2/10 or 1/5.
Now it gets interesting,
The marbles are not returned to the bag after drawing. What is the probability that the second marble is gray?
So, the issue I have is if the first marble drawn is gray, then the probability that the second marble is gray will be different than if a different color was drawn first.
Can anyone help me figure out the probability of the second marble being gray?
Thanks,
Brian
Anyway, we are trying to calculate the probability of an event after an a previous event has already happened.
One example could be something like this:
There are 10 marbles, 2 white, 5 black, and 3 gray
Question, what is the probability of drawing a white marble from a bag if all marbles are put in the bag at the start? Ok, this one is easy, it is 2/10 or 1/5.
Now it gets interesting,
The marbles are not returned to the bag after drawing. What is the probability that the second marble is gray?
So, the issue I have is if the first marble drawn is gray, then the probability that the second marble is gray will be different than if a different color was drawn first.
Can anyone help me figure out the probability of the second marble being gray?
Thanks,
Brian