Question 190784: in a group of 21 people, seven own an ITouch phone. If 9 people are selected at random what is the probability that 5 own an ITouch
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! in a group of 21 people, seven own an ITouch phone. If 9 people are selected at random what is the probability that 5 own an ITouch
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# of ways to select 5 owning an ITouch: 7C5 = 7C2 = 7*6/1*2 = 21
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# of ways to select 4 not owning ITouch: 14C4 = 1001
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# of ways to select 9 without restriction: 21C9 = 293,930
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Probability = [21*1001]/[293,930] = 0.07152
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Cheers,
Stan H.
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