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Leaders and Followers

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by GmatKiss » Sat Aug 06, 2011 12:17 pm
At a motivational forum, a group of 1,500 people are separated into two groups, the Leaders and the Followers. 1,000 people are assigned to the Followers and 500 are assigned to the Leaders. Among these people, there are 75 married couples, each consisting of 1 Leader and 1 Follower. If 1 person is chosen randomly from each group, what is the probability that the two people chosen will be a married couple?

3/20000

1/4500

19/1800

1/75

2/225
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by maihuna » Sat Aug 06, 2011 12:30 pm
it shud be: 75/1000*500 = 3/20000
GmatKiss wrote:At a motivational forum, a group of 1,500 people are separated into two groups, the Leaders and the Followers. 1,000 people are assigned to the Followers and 500 are assigned to the Leaders. Among these people, there are 75 married couples, each consisting of 1 Leader and 1 Follower. If 1 person is chosen randomly from each group, what is the probability that the two people chosen will be a married couple?

3/20000

1/4500

19/1800

1/75

2/225
Charged up again to beat the beast :)
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by edge » Sat Aug 06, 2011 12:31 pm
My answer is A.

P(married leader) = 75/500 = 3/20
P(married follower) = 75/1000
P(particular married follower) = 1/75 (we need this because we have to find the counterpart of the married leader from the followers)

Therefore, P = 3/20 x 75/1000 x 1/75 = 3/20000.
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by ajaykpat » Sun Aug 07, 2011 3:07 am
from question we have information that each group consisting of 75 couple members.

If first we choose from Leaders group then probability of selecting couple = 75C1 / 500C1

now , for section of couple partner in Followers group we have only one choice i.e. = 1/ 1000C1

combining both probability = 75C1 x 1/ 1000C1 x 500C1 = [spoiler]3/20000[/spoiler]

Br,

ajp
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