probability

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klaud: Junior | Next Rank: 30 Posts; Posts: 27; Joined: Sat Jan 28, 2012 8:22 amFollowed by: 1 member

by klaud » Wed Mar 14, 2012 8:10 am

Joshua and John work with 4 other workers. Two of the 6 workers are to be chosen to work on a new project. What is the probability that both Joshua and John will be chosen?

1/6 * 1/5 = 1/30

but the answer is 1/15. Why?

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Source: Beat The GMAT — Problem Solving | Wed Mar 14, 2012 8:10 am

killer1387: Legendary Member; Posts: 581; Joined: Sun Apr 03, 2011 7:53 amFollowed by: 5 members; Thanked: 52 times

by killer1387 » Wed Mar 14, 2012 8:28 am

klaud wrote:Joshua and John work with 4 other workers. Two of the 6 workers are to be chosen to work on a new project. What is the probability that both Joshua and John will be chosen?

1/6 * 1/5 = 1/30

but the answer is 1/15. Why?

select any two=2/6
these two are the required ones= 1/5 (consider the two required as the single body and hence the question turns probability of selecting 1 from 5 i.e. 1/5)

required answer= 2/6*1/5=1/15

HTH

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