<PRE><B>Question 267588</B>
A box contains 30 balls: 20 are red and 10 are blue. 
Five balls are selected at random, without replacement. 
What is the probability that four of them are red? 
P(r = 4) = (20C4*10C1)/30C5 = 4845/27405 = 0.1768
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What if the five balls are selected at random with replacement (i.e, a selected ball is put back in the box before the next selection is made)?
P(r = 4) = 5C4(2/3)^4(1/3) = 0.3292
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Cheers,
Stan H.</PRE>