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Kaplan #26

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Kaplan #26

by magical cook » Wed Aug 22, 2007 5:18 pm
26) If the probability of rain on any given day in city x is 50 percent, what is the probability that it rains on exactly 3 days in a 5-day period?

8/125
2/25
5/16
8/25
3/4


Hi

Can anyone help? Correct answer will follow...
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by devesh » Wed Aug 22, 2007 8:06 pm
select 3 days 5C3

prob of rain for 3 days (1/2)^3

prob no rain for 2 rem days (1/2)^2

hence ans is 5C3*(1/2)^3*(1/2)^2

5/16
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by beny » Thu Aug 23, 2007 6:32 am
5C3 is 10, not 20.
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by magical cook » Thu Aug 23, 2007 6:45 am
OA is C thanks!
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