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# There are 5 locks and 5 keys. What is the minimum number of

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Director
Joined: 14 Sep 2005
Posts: 993
Location: South Korea
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There are 5 locks and 5 keys. What is the minimum number of [#permalink]  24 Nov 2005, 04:41
00:00

Difficulty:

(N/A)

Question Stats:

50% (00:00) correct 50% (00:00) wrong based on 3 sessions
There are 5 locks and 5 keys. What is the minimum number of tries you can find the proper keys for all the 5 locks?

(1) 1
(2) 2
(3) 3
(4) 4
(5) 5
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Auge um Auge, Zahn um Zahn !

SVP
Joined: 24 Sep 2005
Posts: 1891
Followers: 12

Kudos [?]: 159 [0], given: 0

if luck involves ...there're minimumly 4 tries , e.g , you get the correct key for corresponding lock each try right away ...after finding 4 pairs ..the rest will be known without need to try.
Current Student
Joined: 29 Jan 2005
Posts: 5240
Followers: 23

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laxieqv wrote:
if luck involves ...there're minimumly 4 tries , e.g , you get the correct key for corresponding lock each try right away ...after finding 4 pairs ..the rest will be known without need to try.

Laxie always makes these problems appear effortless. Yes, it must be 4 different tries.
Director
Joined: 14 Sep 2005
Posts: 993
Location: South Korea
Followers: 2

Kudos [?]: 49 [0], given: 0

GMATT73 wrote:
laxieqv wrote:
if luck involves ...there're minimumly 4 tries , e.g , you get the correct key for corresponding lock each try right away ...after finding 4 pairs ..the rest will be known without need to try.

Laxie always makes these problems appear effortless. Yes, it must be 4 different tries.

I'm
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Auge um Auge, Zahn um Zahn !

Manager
Joined: 24 Oct 2005
Posts: 52
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Kudos [?]: 5 [0], given: 0

5 locks & 5 keys -- Requires atleast 4 tries..

Yep Ans is 4
VP
Joined: 06 Jun 2004
Posts: 1059
Location: CA
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Kudos [?]: 54 [0], given: 0

Kishore wrote:
Can someone explain how?

As luck would have it, each time you insert a key, it would be the right one.

So we have 5 keys. If from 1st-4th time we inserted a key and it was right, there is no need to try for the 5th time because we already know the one that is left must work.
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