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From a bunch of five keys, three particular keys have to be

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Manager
Manager
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Joined: 18 Dec 2012
Posts: 84
Location: India
Concentration: General Management, Strategy
GMAT 1: 660 Q49 V32
GMAT 2: 530 Q37 V25
GPA: 3.32
WE: Manufacturing and Production (Manufacturing)
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Kudos [?]: 26 [0], given: 20

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From a bunch of five keys, three particular keys have to be [#permalink] New post 13 Oct 2013, 00:31
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A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

76% (01:50) correct 24% (01:25) wrong based on 32 sessions
From a bunch of five keys, three particular keys have to be used to open a combination lock, such that the second key can be used only after the first key and they third key can be used only after the second key. What are the chances of opening the lock in a random selection of three keys?

A. 1/20
B. 1/30
C. 1/60
D. 1/80
E. 1/120
[Reveal] Spoiler: OA

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Re: From a bunch of five keys, three particular keys have to be [#permalink] New post 13 Oct 2013, 01:58
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Expert's post
Qoofi wrote:
From a bunch of five keys, three particular keys have to be used to open a combination lock, such that the second key can be used only after the first key and they third key can be used only after the second key. What are the chances of opening the lock in a random selection of three keys?

A. 1/20
B. 1/30
C. 1/60
D. 1/80
E. 1/120


P = 1/5*1/4*1/3 = 1/60.

Answer: C.
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Re: From a bunch of five keys, three particular keys have to be   [#permalink] 13 Oct 2013, 01:58
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From a bunch of five keys, three particular keys have to be

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