permutation? probability

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jopup: Junior | Next Rank: 30 Posts; Posts: 28; Joined: Sat Jun 14, 2008 5:12 am; Thanked: 1 times

by jopup » Sun Jun 22, 2008 3:05 pm

how do i do this?
6 choose 2?
how do i get probability?

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Source: Beat The GMAT — Problem Solving | Sun Jun 22, 2008 3:05 pm

kishore: Senior | Next Rank: 100 Posts; Posts: 62; Joined: Fri Dec 21, 2007 2:58 pm; Location: Fremont , California; Thanked: 3 times

by kishore » Sun Jun 22, 2008 3:49 pm

Ans) 1/15

Total number of workers = Josua + Jose + 4 = 6

2 people will be interviewed from 6

=> Total outcomes = 6C2

=> Possible outcomes that Josua and Jose are selected = 2C2

Probability = 2C2/6C2 = 1/15

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atlantic: Master | Next Rank: 500 Posts; Posts: 132; Joined: Sun Apr 27, 2008 10:31 am; Location: Portugal; Thanked: 7 times

by atlantic » Mon Jun 23, 2008 12:43 am

Easier way......(I think!!!)

6 workers and among them are Joshua and José.

What's the chance of picking randomly Joshua or José on our first pick? = 2/6 (Joshua or José out of six workers)

What's the chance of picking randmoly Joshua or José, knowing that one of them as already been selected on our first pick, on our second pick?

1/5 (only one good choice available out of 5 workers)

So 2/6*1/5=2/30=1/15

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