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If four people are to be selected from eight people, which

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Manager
Joined: 10 Oct 2005
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If four people are to be selected from eight people, which [#permalink]

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20 Oct 2005, 16:24
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If four people are to be selected from eight people, which include A and B, what is the probability that A is selected but B not?
VP
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20 Oct 2005, 17:17
2/7

Assumption: A is always selected

total combinations: 8C4 = 70

All combinatiosn where A is selected but B is not
Leaving B, there are 7 people from which 4 to be selected
If A is always to be selected, all possible combinations are:
6C3 = 20

required prob = 20/70 or 2/7
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20 Oct 2005, 18:11
= 6C3/8C4 = 20/70 = 2/7
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21 Oct 2005, 07:05
Bang on target.... 6C3/8C4 it is
21 Oct 2005, 07:05
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