Riddles: Thread and Discussions - Page 2
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Carras
Argentina860 Posts
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t3tsubo
Canada682 Posts
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greendestiny
Bosnia-Herzegovina114 Posts
Solution: + Show Spoiler + He needs to start his own fire ahead of the original one and follow it at a leisurely pace of ... ugh I don't know why you put the windspeed because I don't know if I'm supposed to add windspeed to it or not, however if the secondary fire is affected by wind so is the primary, but you said it will take 10 hours for it to burn the whole island, so it can't be. Anyways, that's the answer, minutia is less important. I remember reading a riddle with the same solution as a kid in a book with conundrums and magic tricks called something like "Little smartypants" :-) Where's the father? Solution: + Show Spoiler + On the mother, without a condom! :-) x = 21+y x+6 = 5y+30 This gives y = -3/4 (or -9 months, since we're talking years) Glass Half Full Solution: + Show Spoiler + You tip the glass towards yourself, so the water is almost spilling out. Now observe where the water level ends: if it covers only the bottom of the glass, then it's exactly half full (or empty, as you wish). If the bottom isn't entirely covered, it's less and if it covers the walls then it's more than half. Again, something similar to this was in the same book I mention above, only this time you were going to the market to buy a barrel of wine and the guy selling it swears there is exactly half a barrel left. How will you check if he's telling the truth? Now that I've explained ... day9? Where did you come from? We're doing riddles, come on man, put the glass down ... Sheesh :-) 3 hats Solution: + Show Spoiler + Do you really need a solution? The C dude is wearing a black hat Cork, Bottle, Coin Solution: + Show Spoiler + Ok, usually there is only one solution, but this one has infinite possibilities (I'd blame the wording). For example, riddle doesn't explicitly forbid slicing the bottle in half with a katana, now does it? :-) Edit: removed those sneaky extra tags | ||
ZapRoffo
United States5544 Posts
On December 05 2010 14:13 Aeres wrote: I'm still trying to figure this one out (from Ares[Effort]'s riddle thread): That's because there's absolutely no information given here that could help you figure it out. | ||
t3tsubo
Canada682 Posts
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Emperor_Earth
United States824 Posts
Marble Jars [tag: math, probability, logic] - 2 minutes + Show Spoiler + Put 1 white marble in one jar. Now put 49 white marbles and 50 black marbles in the other jar. Odds of living ~ .5(1) + .5(.49495) ~ 74.4747475% 3 Hats [tag: logic] - 10 minutes + Show Spoiler + Person C is black-hatted. The limiting reagant is the # of white hats. Person A has the largest single bit of information. Let's start with what he sees. If both Person B and C had white hats, Person A would know he's black-hatted. Therefore, Person B & C either have different color hats or are both black-hatted. If Person B sees Person C with a white hat, then Person B knows he's black hatted, since Person B & C can't both have white hats according to Person A. Person C knows that he can't be white-hatted if Person B is white-hatted or Person A would have different observations. Person C also knows that he can't be white-hatted if Person B is black-hatted, or Person B would know what's up. Therefore, Person C can only be black-hatted. Non Homogeneous Rope Burning[tag: math, logic] - 11+ minutes, no idea yet^^, got as far as figuring out 30 minutes.. how can I get a 15 minutes block:D^^ + Show Spoiler + You have two ropes, each of which takes one hour to burn completely. Both of these ropes are non-homogeneous in thickness, meaning that some parts of the ropes are chunkier than other parts of the rope. using these non-homogeneous ropes and a lighter, time 45 minutes. Note: Some clarification on what is meant by non-homogeneous. For instance, maybe a particular section of rope that is 1/8 of the total length is really chunky, and takes 50 minutes to burn off. then it would take 10 minutes to burn off the remaining 7/8, since we know that the whole rope takes an hour to burn off. that's just an example; we don't know any such ratios beforehand. The point is, if you look at one of your ropes and cut it into pieces, you have no clue how long any individual piece will take to burn off. Willywutang and the burning island of doom [tag: logic, thinkoutsidethebox] + Show Spoiler + Willywutang is hanging out on a heavily forested island that's really narrow: it's a narrow strip of land that's ten miles long. let's label one end of the strip A, and the other end B. a fire has started at A, and the fire is moving toward B at the rate of 1 mph. at the same time, there's a 2 mph wind blowing in the direction from A toward B. what can Willywutang do to save himself from burning to death?! assume that Willywutang can't swim and there are no boats, jetcopters, teleportation devices, etc.. (if he does nothing, Willywutang will be toast after at most 10 hours, since 10 miles / 1 mph = 10 hours) Footsize and Spelling Ability [tag: thinkoutsidethebox] + Show Spoiler + Scientific studies have shown that there is a direct, positive correlation between foot size and performance in spelling bees / spelling tests. How can you explain this correlation? Cork, Bottle, Coin [tag: thinkoutsidethebox] + Show Spoiler + If you were to put a coin into an empty bottle and then insert a cork in the bottle's opening, how could you remove the coin without taking out the cork or breaking the bottle? Glass Half Full [tag: math] + Show Spoiler + You are in an empty room and you have a transparent glass of water. The glass is a right cylinder, and it looks like it's half full, but you're not sure. How can you accurately figure out whether the glass is half full, more than half full, or less than half full? You have no ruler or writing utensils. Hint: + Show Spoiler + tagged math because geometry is math. Faustian Round Table Game [tag: logic] + Show Spoiler + You die and the devil says he'll let you go to heaven if you beat him in a game. the devil sits you down at a round table. He gives himself and you a huge pile of quarters. He says "ok, we'll take turns putting quarters down, no overlapping allowed, and the quarters must rest on the table surface. the first guy who can't put a quarter down loses." you guys are about to start playing, and the devil says that he'll go first. however, at this point you immediately interject, and ask if you can go first instead. you make this interjection because you are very smart, and you know that if you go first, you can guarantee victory. explain how you can guarantee victory. Note: If you can put a quarter down so that it balances on the edge, then so can the devil Red Eyes and Blue Eyes [tag: logic] + Show Spoiler + There is an island of monks where everyone has either brown eyes or red eyes. Monks who have red eyes are cursed, and are supposed to commit suicide at midnight. However, no one ever talks about what color eyes they have, because the monks have a vow of silence. Also, there are no reflective surfaces on the whole island. Thus, no one knows their own eye color; they can only see the eye colors of other people, and not say anything about them. Life goes on, with brown-eyed monks and red-eyed monks living happily together in peace, and no one ever committing suicide. Then one day a tourist visits the island monastery, and, not knowing that he's not supposed to talk about eyes, he states the observation "At least one of you has red eyes." Having acquired this new information, something dramatic happens among the monks. What happens? Where's the father? [tag: math, thinkoutsidethebox] + Show Spoiler + The mother is 21 years older than the child. In 6 years from now, the mother will be 5 times as old as the child. Question: Where's the father? Three lightbulbs[tag: thinkoutsidethebox] + Show Spoiler + You are in a room with three light switches, each of which controls one of three light bulbs in the next room. Your task is to determine which switch controls which bulb. All lights are initially off, and you can't see into one room from the other. You are allowed only one chance to enter the room with the light bulbs. How can you determine which lightswitch goes with which light bulb? Manholes + Show Spoiler + Why are manholes round? Forcefield Detainment [tag: logic] + Show Spoiler + A group of prisoners are trapped in a forcefield. These prisoners are perfectly brave, meaning that they would attempt an escape on any positive probability of success. The prisoners are monitored by a guard who has only one bullet in his gun, but who also has perfect marksmanship skills (he never misses). A maintenance technician needs to tune up the forcefield generator, and so for one second, the forcefield is released. How can the guard still keep all the prisoners detained? Note: The prisoners are amoral, so they will back out of agreements with each other made a priori if they are sure they will be the one dying. Also, assume no prisoner can be manhandled out of the forcefield radius by the other prisoners. Lemming Drownings[tag: logic] + Show Spoiler + Somewhere in Northern Eurasia, a group of 20 lemmings is planning a special group suicide this year. Each of the lemmings will be placed in a random position along a thin, 100 meter long plank of wood which is floating in the sea. Each lemming is equally likely to be facing either end of the plank. At time t=0, all the lemmings walk forward at a slow speed of 1 meter per minute. If a lemming bumps into another lemming, the two both reverse directions. If a lemming falls off the plank, he drowns. What is the longest time that must elapse till all the lemmings have drowned? Hint: + Show Spoiler + After making a certain observation, you'll find the calculations trivial Infinite Quarters [tag: math, logic] + Show Spoiler + You are wearing a blindfold and thick gloves. An infinite number of quarters are laid out before you on a table of infinite area. Someone tells you that 20 of these quarters are tails and the rest are heads. He says that if you can split the quarters into 2 piles where the number of tails quarters is the same in both piles, then you win all of the quarters. You are allowed to move the quarters and to flip them over, but you can never tell what state a quarter is currently in (the blindfold prevents you from seeing, and the gloves prevent you from feeling which side is heads or tails). How do you partition the quarters so that you can win them all? 12 balls [tag: math, logic] + Show Spoiler + You have 12 identical-looking balls. One of these balls has a different weight from all the others. You also have a two-pan balance for comparing weights. Using the balance only 3 times, how can you determine which ball has the unique weight, and also determine whether it is heavier or lighter than the others? Coin Machine Weighing [tag: math, logic] + Show Spoiler + You have 12 identical-looking balls. One of these balls has a different weight from all the others. You also have a two-pan balance for comparing weights. Using the balance in the smallest number of times possible, determine which ball has the unique weight, and also determine whether it is heavier or lighter than the others. | ||
annul
United States2841 Posts
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rotinegg
United States1719 Posts
=========================================== + Show Spoiler + Circles are the only shape of a hole where a slightly larger cover is guaranteed not to fall into it. All other shapes, you can rotate the cover a certain way to make it fall into the hole. Three lightbulbs[tag: thinkoutsidethebox] + Show Spoiler + You are in a room with three light switches, each of which controls one of three light bulbs in the next room. Your task is to determine which switch controls which bulb. All lights are initially off, and you can't see into one room from the other. You are allowed only one chance to enter the room with the light bulbs. How can you determine which lightswitch goes with which light bulb? + Show Spoiler + Leave one of them on for a long time, then turn it off and turn on another switch and enter the room. The one that is currently lit is obvious, then feel the two other lightbulbs, the one you left on for a long time will still be hot. | ||
Trion
Canada291 Posts
You are wearing a blindfold and thick gloves. An infinite number of quarters are laid out before you on a table of infinite area. Someone tells you that 20 of these quarters are tails and the rest are heads. He says that if you can split the quarters into 2 piles where the number of tails quarters is the same in both piles, then you win all of the quarters. You are allowed to move the quarters and to flip them over, but you can never tell what state a quarter is currently in (the blindfold prevents you from seeing, and the gloves prevent you from feeling which side is heads or tails). How do you partition the quarters so that you can win them all? + Show Spoiler + Flip all the quarters over, then divide the table how ever you want. If the table and the amount of quarters are infinite then on either side of the split there should be an infinite amount of tails. | ||
t3tsubo
Canada682 Posts
On December 05 2010 15:49 Trion wrote: Infinite Quarters [tag: math, logic]+ Show Spoiler + You are wearing a blindfold and thick gloves. An infinite number of quarters are laid out before you on a table of infinite area. Someone tells you that 20 of these quarters are tails and the rest are heads. He says that if you can split the quarters into 2 piles where the number of tails quarters is the same in both piles, then you win all of the quarters. You are allowed to move the quarters and to flip them over, but you can never tell what state a quarter is currently in (the blindfold prevents you from seeing, and the gloves prevent you from feeling which side is heads or tails). How do you partition the quarters so that you can win them all? + Show Spoiler + Flip all the quarters over, then divide the table how ever you want. If the table and the amount of quarters are infinite then on either side of the split there should be an infinite amount of tails. On December 05 2010 15:45 annul wrote: infinite quarters: flip all quarters. split pile anywhere. cardinality is the same: aleph null on both sides. fixed: now there are only a very large, but finite number of quarters. Theres still a simple way to solve this. Also fixed the coin machine riddle repeat. | ||
Trion
Canada291 Posts
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jeeneeus
1168 Posts
The apple truck and apple-eating squirrel + Show Spoiler + There is an apple truck that can hold up to 1000 apples at any given time. It needs to make a delivery of 4000 apples from town A to B, which is 900 miles apart. However, there is a squirrel living in the truck that will eat 1 apple per mile. for example, if you load 1000 apples and take 4 trips, you will end up with 4x100 = 400 apples left. Try to maximize the number of apples you can deliver. Hint:+ Show Spoiler + You can leave apples on the road along the way, and pick them up whenever you want, assuming your truck has the capacity to hold them. + Show Spoiler + Load up 1000 apples. Drive 250 miles, and take out the remaining 750. Then drive back and do the same thing three more times. At that point, you would have lost 250x4=1000 apples, leaving you with 3000 apples. Then load up 1000 apples and drive 333 miles. Leave the remaining 667, and drive back and repeat two more times. At this point, you would have lost an additional 999 apples, leaving you with 2001. Load up 1000 apples and drive the remaining 900-250-333=317 miles. Go back and do it again with another 1000 apples (sadly there's no way to save that last apple, I suggest you go ahead and eat it since this is a lot of work to be doing). Along the way you would have lost 317x2=634 apples. 2000-634=1366 apples. | ||
Derminator
27 Posts
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Deleted User 3420
24492 Posts
i dont like doing them unless i can be the first to answer them lol | ||
rotinegg
United States1719 Posts
On December 05 2010 16:01 travis wrote: so which riddles havent been solved so far? i dont like doing them unless i can be the first to answer them lol two of mine haven't been solved, they're in the second reply to OP edit: The blind man and checker board + Show Spoiler + This is a two part question. Only open the second spoiler if you are 90% sure you have the correct solution to the first part.A blind man is given a square checkerboard with 4 squares. Each square has a coin on it, and he is told that during each 'turn', he can flip as many coins as he wants. His goal is to make sure that at some point in time, all four of the coins were facing the same way (eg all heads or all tails). He will be given as many of these 'turns' as he wants, but he must try to guarantee a solution in the least amount of turns as possible. How many turns does he need to guarantee that at some point in time, all four coins were facing the same direction?+ Show Spoiler + Congrats, now this time, he is given a harder task: in between each turn, a stranger will come and rotate the checkerboard however he wants to. The stranger can decide not to rotate it at all if he wants. The blind man will obviously have no indication of how or whether the board was rotated at all. The blind man is asked to guarantee a solution in the same manner as the first part. Hint:+ Show Spoiler + Part 2 can be completed in the same number of turns as part 1 The mars robots (Some computer science knowledge required) + Show Spoiler + NASA is trying to launch two robots onto mars so they can construct a station. This is a two robot job, so both robots must work together to build the station. However, they do not have a spaceship big enough to fit both, so decide to launch them separately. Although both rockets will be following the same launch protocols, some error will be inevitable and the robots will land in different positions. Now assume that mars is an endless array of trillions and zillions of squares, stretched side-by-side. Basically, it is an infinite one-dimensional space. Your goal is to program the same algorithm on both robots so when they land, they will start looking for each other, and construct the station together. The robots CANNOT be programmed with different algorithms, and have no means of communication to earth or each other or any entity whatsoever. However, the robots will deploy a parachute when landing, and that parachute will remain in the square they land forever. The robot can detect whether they have found a parachute in the square it is in. Come up with an algorithm so that they will be guaranteed to find each other. (Normal restrictions in programming apply, such as integer overflow: any number larger than 2^32 will be undefined, so if you are keeping a counter and it reaches above that, it will render your algorithm useless.) quoted per your convenience | ||
Trion
Canada291 Posts
On December 05 2010 16:01 travis wrote: so which riddles havent been solved so far? i dont like doing them unless i can be the first to answer them lol Three lightbulbs[tag: thinkoutsidethebox] Forcefield Detainment [tag: logic] Lemming Drownings[tag: logic] Infinite Quarters [tag: math, logic] (now finite) + Show Spoiler + 12 balls [tag: math, logic] The blind man and checker board The mars robots (Some computer science knowledge required) | ||
Trion
Canada291 Posts
you have 20 coin machines, each of which produce the same kind of coin. you know how much a coin is supposed to weigh. one of the machines is defective, in that every coin it produces weighs 1 ounce less than it is supposed to. you also have an electronic weighing machine. how can you determine which of the 20 machines is defective with only one weighing? (by one use, we mean you put a bunch of stuff on the machine and read a number, and that's it -- you not allowed to accumulate weight onto the machine and watch the numbers ascend, because that's just like multiple weighings). you are allowed to crank out as many coins from each machine as you like. + Show Spoiler + 1.label each machine 1-20. 2.Get one coin for the first machine 2 from the second 3 from the third ect. 3.Weigh them all 4. If it is one ounce to light then it is machine one, if it is 2 ounces to light it is machine to, if it is 3 ounces to light it the third machine, ect. | ||
BlackJack
United States9272 Posts
- Hide Spoiler - [/spoiler]You are wearing a blindfold and thick gloves. An infinite number of quarters are laid out before you on a table of infinite area. Someone tells you that 20 of these quarters are tails and the rest are heads. He says that if you can split the quarters into 2 piles where the number of tails quarters is the same in both piles, then you win all of the quarters. You are allowed to move the quarters and to flip them over, but you can never tell what state a quarter is currently in (the blindfold prevents you from seeing, and the gloves prevent you from feeling which side is heads or tails). How do you partition the quarters so that you can win them all?[/spoiler] + Show Spoiler + Just grab 20 quarters and flip them over into the 2nd pile. Even if you grab some tails quarters you will be flipping them to heads so they are removed from both sides. | ||
ZapRoffo
United States5544 Posts
+ Show Spoiler + Because if he always shoots at the one that moves toward escaping first, then he doesn't have to do anything, none of them will move. I guess my answer is: + Show Spoiler + The guard has to say "I will shoot at the first person who moves when the force field is deactivated." But then that might not work because the prisoners might not believe him, and that gives them a positive probability of escaping. | ||
t3tsubo
Canada682 Posts
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