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# M07 q18

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Manager
Joined: 13 May 2010
Posts: 122

Kudos [?]: 24 [0], given: 4

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22 Jun 2012, 05:41
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There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?

(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.

(1) From any two snakes from Pandora's box at least one is a viper. Since from ANY two snakes one is a viper then there can not be 2 (or more) cobras and since there is at least one cobra then there must be exactly one cobra in the box. Sufficient.

(2) The total number of snakes Pandora's box is 99. Clearly insufficient.

Can someone please explain me the solution?

Kudos [?]: 24 [0], given: 4

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 129094 [0], given: 12194

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22 Jun 2012, 05:48
teal wrote:
There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?

From any two snakes from Pandora's box at least one is a viper.
The total number of snakes Pandora's box is 99.

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
EACH statement ALONE is sufficient
Statements (1) and (2) TOGETHER are NOT sufficient

(1) From any two snakes from Pandora's box at least one is a viper. Since from ANY two snakes one is a viper then there can not be 2 (or more) cobras and since there is at least one cobra then there must be exactly one cobra in the box. Sufficient.

(2) The total number of snakes Pandora's box is 99. Clearly insufficient.

Can someone please explain me the solution?

Can you please specify what didn't you understand?
_________________

Kudos [?]: 129094 [0], given: 12194

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 129094 [0], given: 12194

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22 Jun 2012, 09:03
teal wrote:
There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?

(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.

(1) From any two snakes from Pandora's box at least one is a viper. Since from ANY two snakes one is a viper then there can not be 2 (or more) cobras and since there is at least one cobra then there must be exactly one cobra in the box. Sufficient.

(2) The total number of snakes Pandora's box is 99. Clearly insufficient.

Can someone please explain me the solution?

This question is also discussed in the following posts:
devil-s-dozen-129312-20.html?hilit=viper#p1063888
devil-s-dozen-129312-20.html?hilit=viper#p1064475

Hope it helps.
_________________

Kudos [?]: 129094 [0], given: 12194

Joined: 29 Mar 2012
Posts: 322

Kudos [?]: 515 [1], given: 23

Location: India
GMAT 1: 640 Q50 V26
GMAT 2: 660 Q50 V28
GMAT 3: 730 Q50 V38

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24 Jun 2012, 20:54
1
KUDOS
teal wrote:
There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?

(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.

(1) From any two snakes from Pandora's box at least one is a viper. Since from ANY two snakes one is a viper then there can not be 2 (or more) cobras and since there is at least one cobra then there must be exactly one cobra in the box. Sufficient.

(2) The total number of snakes Pandora's box is 99. Clearly insufficient.

Can someone please explain me the solution?

Hi,

Consider the following case, V-Viper, C- Cobra,
(C, C, V, V), from this we can have a pair (V, V), (C, V) which satisfy the condition given in statement 1.
but the pair (C, C) has no viper (there should be at least one viper in any pair!), so such pair is not possible.
Thus, there can be only 1 cobra, along with any number of vipers. Sufficient.

Regards,

Kudos [?]: 515 [1], given: 23

Manager
Joined: 06 Oct 2009
Posts: 104

Kudos [?]: 183 [0], given: 4

Location: Mexico
Concentration: Entrepreneurship, Finance
GPA: 3.85
WE: Sales (Commercial Banking)

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10 Jul 2012, 04:16
I think this question could be enhanced if it states that the Pandora Box has only two kind of snakes.

Kudos [?]: 183 [0], given: 4

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 129094 [0], given: 12194

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10 Jul 2012, 04:26
Bull78 wrote:
I think this question could be enhanced if it states that the Pandora Box has only two kind of snakes.

That's not necessary at all. Check this: devil-s-dozen-129312-20.html?hilit=viper#p1064475
_________________

Kudos [?]: 129094 [0], given: 12194

Manager
Joined: 06 Oct 2009
Posts: 104

Kudos [?]: 183 [0], given: 4

Location: Mexico
Concentration: Entrepreneurship, Finance
GPA: 3.85
WE: Sales (Commercial Banking)

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10 Jul 2012, 04:49
Bunuel wrote:
Bull78 wrote:
I think this question could be enhanced if it states that the Pandora Box has only two kind of snakes.

That's not necessary at all. Check this: devil-s-dozen-129312-20.html?hilit=viper#p1064475

Many thanks Bunuel! U rule!

Kudos [?]: 183 [0], given: 4

Re: M07 q18   [#permalink] 10 Jul 2012, 04:49
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# M07 q18

Moderator: Bunuel

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