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If the coin is tossed 5 times, what is the probability that [#permalink]
21 Jul 2003, 16:50

If the coin is tossed 5 times, what is the probability that at least 3 out of 5 times it will show heads? (Binominal Distribution)
There are 2 green, 3 red, and 2 blue balls in a box. 4 are drawn at random without replacement. What is the probability that of the 4 drawn balls two are red, 1 is green, and 1 is blue? (Hypergeometric Distribution)

With Calculations.. [#permalink]
22 Jul 2003, 06:02

So with calculations (since we will need to do this on the actual test - the more practice now the better!!)

1) 5C3/32 + 5C4/32 + 1/32 = 16/32 = 1/2

Makes sense because the possible numbers of heads are: 0,1,2,3,4 or 5.
Considering the cases 3,4, and 5, we have half of those cases so the prob is 1/2.

2) (2C1 * 3C2 * 2C1)/7C4 = 2*3*2/35 = 12/35

Hope that would be one of the answer choices on the test!