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Probability - MGMAT

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Probability - MGMAT

by GAMATO » Thu Jul 21, 2011 10:26 am
Five A-list actresses are vying for the three leading roles in the new film, "Catfight in Denmark." The actresses are Julia Robards, Meryl Strep, Sally Fieldstone, lauren Bake-all, and Hallie Strawberry. Assuming that no actress has any advantage in getting any role, what is the probability that Julia and Hallie will star in the film together?

[spoiler]OA is 3/10.[/spoiler] Can someone please explain how to approach such problems. My approach was P(Julia AND Hallie will star) = P(Julia will star)* P(Hallie will star) = 1/5*1/4 = 1/20. What am I missing here??
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Source: — Data Sufficiency |
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by vinni.k » Thu Jul 21, 2011 10:53 am
Hi GAMATO,

It is important to know that whatever happens in this movie whether good or bad, "Julia and Hallie" will definitely star together.

Julia, Hallie,___________(now one place is left, so each one of the remaining actresses can join them)
Julia, Hallie, Sally
Julia, Hallie, Meryl
Julia, Hallie, Lauren

So, there are three possible combinations in which Julia, Hallie and others can star together.

Now if you understand combinations then don't think about the constraint and select 3 actresses from the group of 5 i.e 5C3 = 10 to get the total combinations (assuming we are not concerned which actress is given which role)

Probability Julia and Hallie will star together is 3/10 (answer)


Hope this helps

Thanks & Regards
Vinni
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