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.

From any two snakes from Pandora’s box at least one is a viper. This means: You can never pick 2 cobras together. So there can be at most 1 cobra in the box. We’re also told there’s at least 1 cobra; Therefore, there is exactly 1 cobra .

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VANU2

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29 Sep 2025, 06:49

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From any two snakes from Pandora’s box at least one is a viper.
This means:

You can never pick 2 cobras together.
So there can be at most 1 cobra in the box.

We’re also told there’s at least 1 cobra; Therefore, there is exactly 1 cobra.

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16 Oct 2025, 15:47

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Does anyone have any more questions like this?

Bunuel

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17 Oct 2025, 00:18

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FernandaAmorim

Does anyone have any more questions like this?

You can try checking word problems in DS; however, this one is quite unique.

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27 Oct 2025, 03:53

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I did not quite understand the solution. I don't understand the following "This means that there cannot be two or more cobras in the box, because if there were, then we could choose two cobras and that would contradict the statement. Therefore, there must be at most one cobra in the box."

If from any 2 snakes, at least 1 is a viper, why couldn't we have 6 snakes and at least 3 are viper for example. I don't get the logic.

Bunuel

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27 Oct 2025, 04:13

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sjkskjka

The rule says that every possible pair of snakes must contain a viper. If you had two cobras, those two cobras together would form a pair without any viper, which breaks the rule. So only one cobra can exist, even if there are many vipers.

This is a tricky logical problem that has been discussed in detail across several pages. Please review those discussions for a clearer understanding.

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03 Nov 2025, 15:41

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Hi,

Is it correct to say that one is sure that there is only 1 cobra because of the way the ratio is expressed in the statement 1. What I mean is that it says "from any 2 snakes" and not from every 2 snakes"

The words "from any" guarantees us that there are only 2 snakes, and that 1 of them is a Cobra

Am I correct?

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Juan C. Avellan

Bunuel

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04 Nov 2025, 00:04

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avellanjc

“From any two snakes” does not mean there are only two snakes. It means whichever two snakes you pick out of however many are in the box, at least one of those two will be a viper.

So the logic is this: if there were two or more cobras, you could pick those two cobras, and then your pair would have no viper, violating the statement. That’s why there can be only one cobra, not because “from any” limits the total to two snakes, but because the condition applies to every possible pair.

Please study the discussion on previous pages for more.

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07 Nov 2025, 02:17

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I like the solution - it’s helpful. Nice logical question

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03 Jan 2026, 06:31

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Honestly one of the trickiest DI questions I have encountered so far, took me a while to figure out even with the explanation - kudos!

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16 Feb 2026, 17:44

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I think this is the trickiest question I have ever encountered in DI.

Anyone got this right in the first try, must be obtained 90%+ percentile on GMAT, or even 95% I bet