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Probability - Office floor

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by Tryingmybest » Wed Mar 25, 2009 5:52 am
Out of eight marketers and two developers, four people will be chosen at random to occupy the worst office on the floor. What is the probability that at least one of the developers will be chosen?

1/4 1/3 2/5 2/3 3/4

OA D
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by Mustang » Wed Mar 25, 2009 8:54 am
At least 1 developer is chosen means: 1 devloper 3 marketers are chosen or 2 developers and 2 marketers are chosen

probability to chose atleast 1 developer is = (ways to chose 1 developer + ways to chose 2 developer) / (total number of ways to chose 4 people out of 10)

= ((2c1*8c3) + (2c2*8c2))/ (10c4)

= (112+ 28)/ 210

=140/210

= 2/3
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by vittalgmat » Tue Mar 31, 2009 12:09 am
Another method:
P(choosing atleast 1 Developer) = 1 - P(choosing ALL 4 marketers)
= 1 - (8/10 * 7/9 * 6/8 *5/7)
= 1 - 1/3
= 2/3


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Re: Probability - Office floor

by El Cucu » Tue Mar 31, 2009 6:08 pm
Tryingmybest wrote:Out of eight marketers and two developers, four people will be chosen at random to occupy the worst office on the floor. What is the probability that at least one of the developers will be chosen?

1/4 1/3 2/5 2/3 3/4

OA D
(Total combinations - Total combinations of marketers) / total combinations
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