SOLUTION: Two boxes contain parts. The first box has 9 parts, of which 8 are standard. The second box has 4 parts, with 1 being non-standard. One part from the first box is transferred to th

Algebra ->  Probability-and-statistics -> SOLUTION: Two boxes contain parts. The first box has 9 parts, of which 8 are standard. The second box has 4 parts, with 1 being non-standard. One part from the first box is transferred to th      Log On


   

Question 1204804: Two boxes contain parts. The first box has 9 parts, of which 8 are standard. The second box has 4 parts, with 1 being non-standard. One part from the first box is transferred to the second box, and then three parts are taken from the second box. What is the probability that all three parts taken will be standard?
Found 2 solutions by Edwin McCravy, mccravyedwin:
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
I had some errors in drawing my tree diagram. I have fixed them 
and reposted the corrected version below.

Edwin

Answer by mccravyedwin(408) About Me  (Show Source):
You can put this solution on YOUR website!
You should make a tree diagram like this:



Notice that the sum of the probabilities on the far right is 1.
4%2F15%2B28%2F45%2B1%2F90%2B1%2F15%2B1%2F30%22%22=%22%221.
There are 2 cases where he gets 3 standards, the top one with probability
4/15 and the third one down with probability 1/90.

So the probability that all three parts taken will be standard is

4/15 + 1/90 = 5/18.  I did not explain here how I got some of those
probabilities.  If you have any questions, ask me in the thank-you note
space below.

Edwin