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M07 q18

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M07 q18 [#permalink] New post 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?
[Reveal] Spoiler: OA
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Re: M07 q18 [#permalink] New post 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?
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Re: M07 q18 [#permalink] New post 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.
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Re: M07 q18 [#permalink] New post 24 Jun 2012, 20:54
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.

Answer (A).

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Re: M07 q18 [#permalink] New post 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.
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Re: M07 q18 [#permalink] New post 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
_________________

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!


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