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M07-18

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Re: M07-18 [#permalink]

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New post 10 Jul 2016, 01:39
Hi Bunuel, I think the wording - from any two snakes at least one is viper is the trick. Had it been from any three at least one is viper then I think it wont be sufficient. Correct?
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New post 10 Jul 2016, 05:17
Hi rakaisraka,

exactly. Because the first statement clearly informs us that at least one is a cobra and one a viper, that means if there were 2 only and if one is a viper the other one must be a cobra. So for those type of questions, it is crucial to NOT ignore the initial statement.

Bunuel, correct?

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Re M07-18 [#permalink]

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New post 12 Jul 2016, 08:03
I think this is a high-quality question and I agree with explanation.

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Re M07-18 [#permalink]

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New post 20 Jul 2016, 22:32
I think this is a high-quality question and I agree with explanation.

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Re: M07-18 [#permalink]

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New post 23 Jul 2016, 16:00
Hi!
Just to ask...
st 1 says atleast... so there could me one... and more also..
how can we stick to just one question..
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M07-18 [#permalink]

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New post 03 Aug 2016, 08:52
dukenukem wrote:
Bunuel wrote:
KPMM07 wrote:
I think this question is poor and not helpful.


Please elaborate on this. The question is perfectly valid, though quite hard.


Interesting solution, but not sure how this is math (not counting/probability/algebra/arithmetic etc.)
More like it was a question testing your logical deduction.


I agree with you!

http://lsatblog.blogspot.com.br/2011/02 ... -some.html

One thing that got me to this question is the meaning of at least which means some ranging from few, several or many up to "all".

So, if "at least" ranges from 1 to "all",

but "all" is unreachable for every two pairs - because the constraint from the question stem said c>=1,

then the remaining is "at most."

Now, stretch the logic and test it to a greater number of "snakes". :!:

Is this a 800+ question? :shock:
>> !!!

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Re: M07-18 [#permalink]

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New post 21 Sep 2016, 02:41
I think it is a very nice question. It is challenging but it teaches you to very carefully read the questions stems.

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M07-18 [#permalink]

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New post 29 Sep 2016, 15:25
Just to make it simple, statement 1) assumes that possibility of getting 2 cobras when choosing a pair = 0.

From the question stem, there must be at least one cobra in the box. Therefore, at minimum, there must be 1 cobra.

However, if there were more than 1 cobra, there is still a chance to pick 2 cobras no matter how many vipers there are.

Even if we have 1,000 vipers to 2 cobras, probability of picking a pair and ending up with 2 cobras is not 0, although it's quite close to it.

Since statement says that you are getting at least one viper, it means that there can only be one cobra.

For example, if you had 1,000 vipers and 2 cobras and you picked 1 cobra.

Now the probability of picking another cobra becomes 1/1001 (1001 = 1000 vipers + 2 cobras - 1 cobra which was just picked). It is still not 0 and you can still end up with 2 cobras in a pair.

Therefore, there can only be 1 cobra.

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Re: M07-18 [#permalink]

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New post 19 Oct 2016, 06:47
I answered this one incorrectly but after reading the explanation it's all become so clear.

Just imagine a box full of snakes - you can see all of them crawling there. Try and take 2 cobras out of it - you won't be able to because it will violate Statement (1). You can only take 1 cobra out. There can't be 0 cobras either based on the same statement. Therefore, 1 cobra.

A very nice question IMHO.

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Re: M07-18 [#permalink]

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New post 13 Nov 2016, 05:12
I think it is a very good question that makes you think, I got it wrong but after reading through the discussion, it was clear. Just as a deduction:
Would it mean that there are only two cobras if the first statement was:
From any three snakes, there is at least one viper .......

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Re M07-18 [#permalink]

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New post 28 Nov 2016, 22:25
I think this is a high-quality question and the explanation isn't clear enough, please elaborate. I get that since out of the two snakes picked atleast one is viper. That makes another pick a cobra for sure. But this does not tell me about the number of cobras that the pandora box has.

According to the solution I agree that 1 cobra is for sure, but there could be 2, 3, . . 9, 10, 11 . . 100, etc out which one cobra, definitly, finds a place in the pic.

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Re: M07-18 [#permalink]

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New post 28 Nov 2016, 22:29
rajeshkpandey wrote:
I think this is a high-quality question and the explanation isn't clear enough, please elaborate. I get that since out of the two snakes picked atleast one is viper. That makes another pick a cobra for sure. But this does not tell me about the number of cobras that the pandora box has.

According to the solution I agree that 1 cobra is for sure, but there could be 2, 3, . . 9, 10, 11 . . 100, etc out which one cobra, definitly, finds a place in the pic.


How can there be more than 1 cobra if from ANY two snakes from Pandora's box at least one is a viper?

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Re M07-18 [#permalink]

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New post 11 Jan 2017, 11:52
I think this is a high-quality question and I agree with explanation.

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Re: M07-18 [#permalink]

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New post 10 Feb 2017, 23:14
This is a Brilliant question.

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New post 14 Mar 2017, 10:51
I am still confused. The question states there is at least 1 cobra and 1 viper, and asks about the number of cobras.
(1) says From any two snakes from Pandora's box at least one is a viper.
This means at most, there is 1 cobra from any two snakes. But we are still missing the total number of snakes, and "At least 1" does not mean "it is 1". What am I missing?

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Re: M07-18 [#permalink]

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New post 14 Mar 2017, 11:56
mitko20m wrote:
I am still confused. The question states there is at least 1 cobra and 1 viper, and asks about the number of cobras.
(1) says From any two snakes from Pandora's box at least one is a viper.
This means at most, there is 1 cobra from any two snakes. But we are still missing the total number of snakes, and "At least 1" does not mean "it is 1". What am I missing?


This is a hard logical question.

(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 cannot be 2 (or more) cobras and since there is at least one cobra then there must be exactly one cobra in the box. Sufficient.
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New post 14 Mar 2017, 12:23
Got it, thank you for highlighting "Any" - it helped.

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M07-18 [#permalink]

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New post 16 Mar 2017, 01:57
Bunuel wrote:
Official Solution:

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 in Pandora's box is 99.


This is a hard question that challenges test-taker's logic. It is simple once you understand it but hard if you have never solved it. If you made a mistake on this question, make sure you understand the logic so you can be armed with this new tool for the real test.

(1) Statement 1 tells us that from any two snakes from Pandora's box at least one is a viper. This does not mean that there are 2 snakes in the box or that there is only 1 viper. Instead, it indicates that at most, there is 1 cobra. This may mean 1 cobra and 1 viper or 1 cobra and 99 vipers. Make sure you understand this distinction. S1 tells us that there is only 1 cobra in the box, which is sufficient.

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


Answer: A


Hi Bunuel,

Kindly help me understand this:

If the question were to be, "how many VIPERS are there?", will (C) be correct in this case?
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Re: M07-18 [#permalink]

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New post 16 Mar 2017, 07:00
duahsolo wrote:
Bunuel wrote:
Official Solution:

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 in Pandora's box is 99.


This is a hard question that challenges test-taker's logic. It is simple once you understand it but hard if you have never solved it. If you made a mistake on this question, make sure you understand the logic so you can be armed with this new tool for the real test.

(1) Statement 1 tells us that from any two snakes from Pandora's box at least one is a viper. This does not mean that there are 2 snakes in the box or that there is only 1 viper. Instead, it indicates that at most, there is 1 cobra. This may mean 1 cobra and 1 viper or 1 cobra and 99 vipers. Make sure you understand this distinction. S1 tells us that there is only 1 cobra in the box, which is sufficient.

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


Answer: A


Hi Bunuel,

Kindly help me understand this:

If the question were to be, "how many VIPERS are there?", will (C) be correct in this case?


Yes. From (1) we have that there is 1 cobra and the rest are vipers, from (2) we have that there are 99 snakes, so there must be 98 vipers.
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Re: M07-18 [#permalink]

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New post 31 Mar 2017, 12:51
I get the solution but what confused me was the possibility of a third type of snake that is NOT viper or Cobra. I thought the question stem left that possibility open

"There is at least one viper and at least one cobra in Pandora's box"- could mean that there is 1 Viper, 1 cobra and another type of snake.....nowhere does it say that the box only contains cobra and vipers

^ If this is the case. Should we always assume that it contains just cobra and viper? I don't remember where but there was a similar question maybe on OG where an answer was not sufficient because you couldn't assume a box only holds X and Y unless it specifically said so

As such, statement A could mean that you can get 1 Viper and 1 Cobra or 1 Viper and a third type of snake, no?

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Re: M07-18   [#permalink] 31 Mar 2017, 12:51

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