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Topic: Easy: Knight and Dragon (Read 19385 times) |
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bob dodge
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A dragon and knight live on an island. This island has seven poisoned wells, numbered 1 to 7. If you drink from a well, you can only save yourself by drinking from a higher numbered well. Well 7 is located at the top of a high mountain, so only the dragon can reach it.
One day they decide that the island isn't big enough for the two of them, and they have a duel. Each of them brings a glass of water to the duel, they exchange glasses, and drink. After the duel, the knight lives and the dragon dies.
Why did the knight live? Why did the dragon die?
Note: From a Trilogy interview.
I haven't solved this one yet. Here is how my thinking goes. The knight presents the dragon with a glass of normal water. The dragon assumes he is getting poisoned water, and immediately runs to well 7, and drinks. He does this because well 7 will neutralize the poison from any tainted well the knight can reach. Now, because he had never poisoned himself before, rather than neutralizing the poison of a lesser well, the water of 7 will kill the dragon, as there is no cure, as there is no well numerically higher than 7.
now, for the knight part. why wouldn't the dragon give the knight well 7 water? if the dragon did give knight well 7 water the knight would die too.
I am suspicious that the dragon agrees to not give well 7 water as the knight cannot reach well 7. Even so, why can't the dragon give the knight water from well 6, in which case the knight would die too.
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yasonf
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Re: Easy: Knight and Dragon
« Reply #1 on: Jul 27th, 2002, 4:22am » |
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here is what I believe to be the solution:
assuming that both the knight and dragon die immediately after the duel, and can't drink another glass of water...
before the duel, the knight drinks from any of the wells (except number 7), then heads to the duel. The knight brings with him a glass of number 1. The dragon, thinking that since only he can get to number 7, brings number 7 to the duel. When they trade glasses, the number 7 that the knight drinks, cancels the number 1 he drank earlier and he is cured. The dragon drinks the number 1 and then dies.
This all assumes that, theoretically, if the duel were done without anything done before hand (i.e. the knight drinking number 1), then they would both die, because neither of them would have access to a higher well immediately. If the poison takes a while to kill you, then the dragon could, in both situations, fly to the 7th well, and drink and live; then they would be back in the same situation as the beginning.
Giz
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Ion Rush
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Re: Easy: Knight and Dragon
« Reply #2 on: Jul 27th, 2002, 4:34am » |
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yea, I posted this earlier but under a different name (I was sloppy with the roll down fields)
yep, I can see that, the knight drinks poison from well 1, but gives clean water, assuming the dragon will immediately go to well 7 and drink thinking he is poisoned.
unfortunately, if the knight can think forward, why can't the dragon, and as the knight predicts the dragon's act of giving him well 7 water and assuming his own cup is tainted, going straitght to 7, why can't the dragon also figure this out. Then the dragon would offer the knight water from well 1, and the dragon would not attempt to neutralize his own poison, has he figures the knight slipped him clean water.
well 1 water would not neutralize poison from well 1, but the knight wouldn't realize this, and die
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Kozo Morimoto
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Re: Easy: Knight and Dragon
« Reply #3 on: Jul 27th, 2002, 6:12am » |
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I can see a scenario where the Dragon can guarantee 100% survival but not for the Knight.
Dragon turns up by drinking from well 1 before hand.
a)
Knight turns up with clean water.
Dragon goes drinks from well 1 (drinking more doesn't do anything), then drinks from well 7.
b)
Knight turns up with water from well 1.
Dragon goes drinks from well 1 (drinking well 1, 3 times won't do anything), then drinks from well 7.
c)
Knight turns up with water from well 2 to 6.
(Dragon is cured now) But Dragon goes and drinks from well 1 to REPOISON himself then drinks from well 7 to neutralize.
So in all scenarios, Dragon drinks from well 1 prior to duel then goes back and drinks from well 1, followed by well 7 to guarantee survival.
However there are no 100% survival scenarios for the Knight.
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yasonf
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Re: Easy: Knight and Dragon
« Reply #4 on: Jul 28th, 2002, 12:38am » |
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OK, here is another idea...
Before the competition, the knight drinks from well 1. The knight brings a glass with water from two wells, lets say wells 1 and 2. The dragon brings a glass of number 7 to the duel. At the duel, they trade and the knight drinks number 7 which nutralizes the number 1 he drank earlier, so he is safe. The dragon drinks the mix if 1 and 2. The dragon then knows that the only way to negate this drink is to go to number 7 well and drink. He drinks number 7 but it only poisons him because the mixture he drank before was a nutralized glass of water.
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Princeton
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Re: Easy: Knight and Dragon
« Reply #5 on: Jul 28th, 2002, 9:19pm » |
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The knight gives the dragon a glass of plain water. The dragon gives the knight water from well 1 through 6. The knight rides on the dragons back up to well 7. They then both drink from well 7. This in fact poisons the dragon, but cures the knight. The problem doesn't say the dragon is smart. Maybe he's too lazy to fly up to the mountain twice in one day, so he just uses well 6, figuring it will kill the knight just as surely as well 7. Folks, ya gotta think outside the box if you want to work at Trilogy.
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jmlyle
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Re: Easy: Knight and Dragon
« Reply #6 on: Jul 28th, 2002, 10:33pm » |
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This is one of those problems that I like to figure out, what is extraneous? Like the Funkytown-hair problem, it might be easier to think about with less information (4 instead of 483,207 works just as well).
I think that 7 wells are many more than are needed. I think that three wells total should provide the exact same situation, but it might require four, if it's more complicated that I'm thinking.
Frankly, the way the question is worded seems far too simple for the problem. The actual question is basically only asking, "What is a sceanrio in which the knight lives and the dragon dies?"
A possible answer to this question is:
Knight drinks water from well 5 before the duel
Knight brings water from well 6
Dragon brings water from well 7
Knight is cured by water from well 7.
Dragon forgets to drink from well 7 and dies.
-- jmlyle
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Tom
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Re: Easy: Knight and Dragon
« Reply #7 on: Jul 30th, 2002, 8:35am » |
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Here's my answer:
The knight drank from well 1 before the duel and took plain water.
The dragon took water from well 7. After the duel he drank from well 7 assuming it would cure him from well 1-6.
The knight was cured by well 7 and the dragon was poisoned by well 7.
The question didn't ask for a scenario in which the knight would always live and the dragon would always die. The question simply wanted to know how it could have happened that the knight lived and the dragon died. There is more than one answer, and none are absolute.
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cnmne
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Re: Easy: Knight and Dragon
« Reply #8 on: Jul 30th, 2002, 1:37pm » |
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I think that the question is simplistic and expects a simplistic answer. The person writing the interview was not as smart as the person they were hiring, so it is a real world example and the interviewee had to account for that. The knight drank water from well 1 before the duel and brought plain water, assuming the dragon would bring water from well 7 and drink well 7 water after. The knight assumes that the powerful dragon has the brains of a bully and turns out to be right.
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Daishi
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Re: Easy: Knight and Dragon
« Reply #9 on: Jul 30th, 2002, 10:29pm » |
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Question: If the knight could bring plain water, why were they drinking from poisoned wells in the first place?
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Blender
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Re: Easy: Knight and Dragon
« Reply #10 on: Jul 31st, 2002, 1:15pm » |
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No problem. The knight drinks a glass of the all-powerful antidote before the duel. He brings a glass of water from well 1. Since all the wells are poison, then the dragon, drinking from 7, still dies. The knight has the antidote and lives.
How does the knight get the antidote? The same way all the rest of you are fabricating the 'plain water' that isn't described in the original riddle.
Now, has anyone solved this with just the items described in the riddle?
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Ion Rush
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Re: Easy: Knight and Dragon
« Reply #11 on: Jul 31st, 2002, 9:11pm » |
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"Knight is cured by water from well 7.
Dragon forgets to drink from well 7 and dies. "
but you are specifically given the information that ONLY the dragon can reach well 7. also, they want to get rid of eachother, enough so they want to kill eachother. why the hell would the dragon carry the knight to well 7
as far as implying nonpoisonous water...you are right, the riddle doesn't say that there is no pure water, but we can infer that their is, otherwise there would be no need for a duel, because each would soon die from dehidration. (drink well 1 on day one, well 2, etc etc, until well 6 or 7 -depending on your flight ability - then what ? die from dehidration. If you can drink from well 1 then neutralize it with water from well 2, you also have access to nonpoisonous water by mixing the 2
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jmlyle
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Re: Easy: Knight and Dragon
« Reply #12 on: Jul 31st, 2002, 11:23pm » |
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Ion, you need to read a little more carefully. You asked:
Quote:why the hell would the dragon carry the knight to well 7
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What I had said was:
Quote:Knight drinks water from well 5 before the duel
Knight brings water from well 6
Dragon brings water from well 7 
Knight is cured by water from well 7.
Dragon forgets to drink from well 7 and dies.
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--jmlyle
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blender
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Re: Easy: Knight and Dragon
« Reply #13 on: Aug 1st, 2002, 8:56am » |
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ok. So if you all are of the opinion that it's safe to fabricate the pure water, then I believe I can solve the riddle in a more obvious and 'clean' way.
Basic tenets:
The riddle says "there are seven poisoned wells".
We accept that there is other pure water available.
Now, since all the wells are poisoned, then it must be the case that anyone drinking from well 7 will be poisoned and since there is no well 8, then they will die. Both knight and Dragon.
So the knight brings pure water _and_ water from some random well. The dragon brings water from some other random well. They switch glasses. The dragon drinks from the glass provided by the knight. The knight drinks some pure water (because the riddle states that the knight does indeed drink something but doesn't say _what_). The dragon realizes he's been poisoned and goes through the various wells, finally drinking from #7 and dies. The knight didn't drink any poisoned water and lives.
Easy.
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jmlyle
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Re: Easy: Knight and Dragon
« Reply #14 on: Aug 1st, 2002, 9:15am » |
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blender, you're kidding, right?
Even if you're not, this doesn't require there being any pure water available at all.
If the knight is able to distract the dragon enough that he can switch glasses to one that he has hidden under his helmet (HEY! What's that behind you?!), then he can just drink a glass of water from 1 and later go over and have a sip from 2.
In fact, he could just distract the dragon again (WAIT! There it is again! Look! I'm serious!), and then swap for yet another glass of water from 2 that he has hidden in his cod piece.
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James G
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Re: Easy: Knight and Dragon
« Reply #15 on: Aug 1st, 2002, 9:09pm » |
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Well...
The way I read the riddle was that drinking from a well, then a higher numbered one cancels the poison completely. ie. both the knight and dragon could live on the island without dehydrating by drinking well 1 water and chasing it up with well 2 water (or chasing up well 3 water with well 6, or well 1 with well 7, or whatever). I don't think there's supposed to be any kind of chain effect, where someone drinks from well 1, then has to drink from 2, then has to drink from 3, etc. After all, if there was, what would be the point in the duel? Both could kill the other. (I know this concept is somewhat bizzare, but I think that's how the riddle is intended.)
But regardless of whether there is any clean water available, I think it would be against the rules of the duel to bring clean water. (That's the way I read it.)
I'm assuming that well 7, which is impossible for the knight to reach, is also time-consuming for the dragon to reach, and that all the other wells are easily accessible. (Not specifically stated in the question, but seems to be implied?)
And I'm assuming that the knight is smarter than the dragon. This seems reasonable, since the knight lived and the dragon didn't, even though the dragon had more resources available.
So... the dragon decided to bring either well 7 or well 6 water. It knew that the knight wouldn't be be able to reach a higher number well, and also knew that whatever water the knight brought, well 7 would neuturalise it.
The knight anticipated the dragon's thinking, brought water from one of wells 1 to 5, and drank a little of it before the duel. (Or maybe got water from well 6, and drank some water from well 1 before the duel, if that's possible. Or maybe got water from well 6, and drank a little of it before the duel, if they assumed the dragon would bring from well 7.) Hence the knight lived.
The dragon, having drank poison water, now heads off for well 7, but dies before getting there. (Or realises they can't make it, and drinks from well 6 instead perhaps, if the knight had brought well 6 water.)
Too many assumptions? It seems plausible though.
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smst
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Re: Easy: Knight and Dragon
« Reply #16 on: Aug 2nd, 2002, 5:29am » |
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No pure water required for this to have worked. To give us the outcome given in the riddle, we just have the knight bring some water from #1-#6 (any one is fine) and the dragon bring some water from a higher well (#7 is ideal). The knight sips some water before they meet, they switch glasses, and the higher-numbered water neutralises anything the knight has already drunk. The low-numbered water kills the dragon (even if he'd sipped some higher-numbered stuff beforehand, it wouldn't have helped).
It seems that we're not being asked to come up with a strategy which guarantees a win for the knight -- just to hypothesise on what could have happened. I reckon the point of the riddle is to get you to say "the knight drank something before the duel", with which will come the zen-like enlightenment that the water drunk during the duel will have become a cure, not a poision.
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kybernetikos
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Re: Easy: Knight and Dragon
« Reply #17 on: Aug 2nd, 2002, 6:23am » |
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Can't the knight guarantee survival by drinking from well #1 before the contest and then after the contest drinking more from well #1, then drinking from well #2.
The dragon can't guarantee survival, because he doesn't know if the knight has poisoned him or not. Even drinking from all the wells in sequence doesn't help, because there's an odd number of wells. The best the dragon can do is 50% chance of survival, while the knight can be sure he'll survive.
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Mortimer
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Re: Easy: Knight and Dragon
« Reply #18 on: Aug 8th, 2002, 1:09am » |
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I'm assuming the dragon's smart, but doesn't understand duplicity. The knight, being human, knows how to cheat.
Tom was the first to post the right answer. Before the duel, the knight drank from any of the wells 1-6, probably 1. The dragon brought 7 to the duel, which the knight then drank as the antidote.
The knight brought plain water to the duel, the dragon believed it was 1-6, so after the duel, the dragon flew back up and drank from well 7, thus killing himself.
How did the knight get plain water? There might be an unpoisoned well around. If not that, he could have possibly mixed the water from well 1 with a higher water. Or he could have simply spat into the cup until it was full. Failing all these, they're on an island. If it's in a fresh water lake, he could just go down to the beach and fill the glass. If it's salt water, he could filter out the fresh water by building a fire, pouring salt water into it, and collecting the steam or something. Or maybe it rained before the duel.
Pick a method, or invent your own. The solution's the only possible one.
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Charlie Dobbie
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Re: Easy: Knight and Dragon
« Reply #19 on: Aug 9th, 2002, 12:59am » |
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My answer is maybe a bit of a cheat, but I submit it here for your approval:
At the duel the Dragon is sure to have brought water from well 7 as it's the only advantage he has. (Assumption 1: The Dragon acts intelligently.) The Knight brings whatever water he can, water from well 1 would do. It doesn't matter.
At the time of the duel, both parties are getting ready to drink. If the duel went ahead like this, both would live immediately after the duel (Assumption 2: The poison's effects are not immediate, as must be if you can be cured,) although both would be poisoned. After the duel, the Knight can drink from any of wells 1-6 to cure himself, while the Dragon can drink from any of wells 1-7. As the Knight cannot reach well 7 it can be considered an antidote to anything the Knight gives the Dragon (Assumption 3: The poisoned party can tell they've been poisoned.) As the Dragon can reach the highest well, the Knight cannot survive if it gets water from there.
My answer is that the Knight raises the glass but does not drink, and when the Dragon raises his water to his lips (Assumption 4: Dragons have lips...), the Knight draws his sword and stabs him.
My thought is that as either party can drink beforehand, and neither party know what water they are presented with, there are many different possible outcomes, none of which yield a guaranteed success for the Knight. Thus, the only way to win is not to play.
How about that?
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Just a guy
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Re: Easy: Knight and Dragon
« Reply #20 on: Aug 13th, 2002, 9:18pm » |
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Ok, the way I figure is that the knight drank from well one before hand knowing well that the dragon would give him water from six or seven. The knight then can bring the dragon water from well 1 or any of the other five he can reach. After they drink, they DUEL, so the dragon has no chance of leaving and going to a well. Then the dragon dies and the knight survives.
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Brian Reynolds
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Re: Easy: Knight and Dragon
« Reply #21 on: Aug 23rd, 2002, 6:54am » |
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I agree with Mortimer -> the problem states that they're on an -island- with seven poisoned wells, so "clean" water is in fact one of the items mentioned in the riddle and "island" is just the sneaky way of getting it in there.
These solutions are supposed to be "elegant" and "sexy" and the clean water solution is just that.
So: Knight sips from well 1 beforehand and gives the dragon a glass of clean water. Dragon gives knight a glass of well 7, which curest the knight, and then rushes to drink from well 7, thinking it will cure him of whatever the knight gave him. But since the knight didn't give the dragon poisoned water, drinking from well 7 -poisons- the dragon, and since there's no higher numbered well, the dragon dies.
This is additionally elegant because it fits with the traditional stereotypes for knights and dragons -- the dragon tries to do the most evil thing possible, and the knight is able to win without having to poison his foe -- the dragon poisons himself!
Okay, so I didn't pee in my pants but it's pretty elegant.
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Re: Easy: Knight and Dragon
« Reply #22 on: Aug 25th, 2002, 12:17am » |
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As others have said, it's possible for both the knight and dragon to guarantee that they will live, even if the opponent will not die. Both drink from well 1 before the dual, bring whatever they want in a glass to the dual, drink the opponents glass, drink again from well 1, and then drink from well 2. This guarantees they never drink a higher poison than they can cure, unless they are drinking the opponents glass which would cure their well 1 poison. The only solution is that the dragon was stupid. Maybe a better riddle would have been "Where did they get the glasses?"
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Marc Nielsen
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Quote:
Charlie Doobie wrote:
My answer is that the Knight raises the glass but does not drink, and when the Dragon raises his water to his lips (Assumption 4: Dragons have lips...), the Knight draws his sword and stabs him. |
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I believe you are correct - the knight draws his sword and kills the dragon
Explanation follows...
Quote:jmlyle wrote:
In fact, he could just distract the dragon again (WAIT! There it is again! Look! I'm serious!), and then swap for yet another glass of water from 2 that he has hidden in his cod piece |
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Although, I wouldn't say that the knight had to switch water you are on the right track. Distraction - or rather misdirection.
If we take a look at the riddle once more (interesting parts hihglighted):
A dragon and knight live on an island. This island has seven poisoned wells, numbered 1 to 7. If you drink from a well, you can only save yourself by drinking from a higher numbered well. Well 7 is located at the top of a high mountain, so only the dragon can reach it.
One day they decide that the island isn't big enough for the two of them, and they have a duel. Each of them brings a glass of water to the duel, they exchange glasses, and drink. After the duel, the knight lives and the dragon dies.
Why did the knight live? Why did the dragon die?
***
Who says that the duel is the exchange of water It could just be plain water (in case they needed refreshment) - the riddle doesn't state that the two parties bring water from a poisened well. The riddle doesn't state that the water exchange is the duel, either (and I don't asssociate a duel with an exchange of water.)
The answer: They drink the water and in the following duel the knight kills the dragon.
Anyway; as we don't get enough information from the riddle (we have to make assumptions) the answer is blowing in the wind. (ie. a given answer just has to be well argued for)
regards Marc Nielsen
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Jeremy
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Re: Easy: Knight and Dragon
« Reply #24 on: Nov 7th, 2002, 5:43am » |
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If you want to cling to that answer, go for it. But it really ignores all the original parameters of the riddle, and makes the same assumptions that the "clever" solution makes.
I hold with Tom's solution. The knight drinks from a poisoned well before hand, and the dragon's glass cures him. The knight brings a non-poisoned glass, and the dragon (thinking he needs to cure himself) drinks from well 7, and dies. No non-poisoned water you say? the night can get some sea water.... i'm sure poisoned water isn’t' supposed to taste good either.
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