Question 528318: Four balls are selected at random without replacement from an urn containing three white balls and five blue balls. Find the probability that two or three of the balls are white. (Round your answer to three decimal places.)
I have tried,
8C4 = 70 for total number of ways
8 because it's the total amount of balls and 4 because thats how many balls are being selected
Then I tried, 4C3=4
4 because thats how many are being selected and 3 because thats how many white balls there are
then i did 4/70 and it was wrong
Answer by scott8148(6628)   (Show Source):
You can put this solution on YOUR website! there are 3 white balls, so there is only one way to select the 3 BUT
___ they are selected along with one blue ball, which can be done in 5 different ways
___ so there are 5 ways to select 3 white balls (and one blue one)
there are 3C2 ways to select 2 white balls, and 5C2 ways to select the 2 blue ones to go with them
___ so there are [(3C2)(5C2)] or 30 ways of selecting 2 white balls
probability of 2 OR 3 white ___ (5 + 30) / 70
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