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# 2 of the 5 production lines are defective. If 2 lines

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Senior Manager
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2 of the 5 production lines are defective. If 2 lines [#permalink]

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03 Feb 2005, 12:56
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2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that both of them are defective?
Senior Manager
Joined: 07 Nov 2004
Posts: 455
Followers: 2

Kudos [?]: 102 [0], given: 0

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03 Feb 2005, 17:29
DLMD wrote:
C (3,2) / C (5,2)

this is OA, heck, I dont' understand neither
SVP
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03 Feb 2005, 21:09
This would be correct is the question is:

2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that none of them are defective?
VP
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03 Feb 2005, 21:24
2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that both of them are defective? (initial post)

-> 1/5 * 1/4 = 1/20

2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that none of them are defective? (Honghu post)

-> 3/5 * 2/4 = 3/10
VP
Joined: 13 Jun 2004
Posts: 1115
Location: London, UK
Schools: Tuck'08
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Kudos [?]: 45 [0], given: 0

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03 Feb 2005, 22:28
sorry, I made a mistake, goes too fast

There are 2 defective production lines
The total of production lines is 5 so we can find that there are 3 productions lines running without any problems.

2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that both of them are defective? (initial post)

shoud be 2/5*1/4 = 1/10

2 of the 5 production lines are defective. If 2 lines selected randomly, what is the probability that none of them are defective? (Honghu post)

3/5*2/4= 3/10

sorry for the mistake
03 Feb 2005, 22:28
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