Eleven weigh exactly the same amount, but one of them is slightly lighter or heavier. If they are equal then. How do you do it? Each islander is given a position to sit on the seesaw for each round. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. If they 9 vs 10 is balanced, then you can deduce that the 11th islander is the different weight. It only takes a minute to sign up. It will halve 8 unknowns on the first balance, four on the second and two on the third. Eleven weigh exactly the same amount, but one of them is slightly lighter or heavier. New comments cannot be posted and votes cannot be cast. Say as example 1234 were lighter. ((, Please explain your claim that is was not asked properly. sorry my bad. @emdee - Here is the link that you posted in the question. The first measurement of 4 vs. 4 was equal. (seesaw measurement number 3), 2.B.3 if right heavy You can figure out both in three steps. Scenario Two, from your original 4x4 weighing: 2. Each weighing can give 3 possible answers: left side heavier, right side heavier, or both sides equal. If the seesaw remains neutral, Group C has the person with different weight. (Detailed . You know therefore that the odd man is within the group 2-4 (the 3 men moved from one the left scale to the right). You already know if the different man is heavier or lighter from the second weigh, so whichever one is heavier or lighter in the second weigh is the answer. In step 3 place one unknown on each side. c) If they are the same, then one of 3,4 is different. Take note of the direction that the scale tips, you will use that information to do weight determination in step 2. Why are non-Western countries siding with China in the UN? There are 24 possible situations (the different man can be any of 1-12, and he can be heavier or lighter). Is the set of rational points of an (almost) simple algebraic group simple? The seesaw will balance perfectly. Puzzling Stack Exchange is a question and answer site for those who create, solve, and study puzzles. All of the islanders individually weigh exactly the same amount, except for one, who either weighs more or less than the other 11. Solution 1a. seesaw: S1 S2 S3 R1 R2 R3 (heavy) The odd man is in the group is in 9-12. Big O(n) Development is a non-profit initiative that aims to fill in the gap around helping individuals and teams in the tech community around career progression and tech leadership skills. A standard see-saw must be used and only three times. Example for condition 1: put three "unknowns" against three "knowns". Happy problem solving. Proceed to solution 1a. Jordan's line about intimate parties in The Great Gatsby? The seesaw will NOT be perfectly balanced. Weigh A against B. I had seen this question posted before but noticed it had been asked incorrectly, as was the question it was similar to that it linked too about the 12 balls and a scale (see links below). now compare R2 and R3. Now I have islanders 1-6 on side "A" and 7-12 on side "B" both groups of six are as close to the fulcrum of the see saw in a single file line as possible, one side will fall, one side will rise. There are 12 men on an island. now switch R1 R2 R3 and S2 S3 S4 AND switch R1 AND L1. You have to figure out which Islander is the heaviest using a seesaw. Another coin weighing puzzle. Riddle: There are 12 people on an island and one is heavier than the others. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. 11 of them weigh the same and one of them is either slightly heavier or slightly lighter. How do you figure out which one is heavier? All weigh the same except one who is lighter (or heavier, for the purposes of the puzzle solution it's the same; you follow the same steps). They each weigh exactly the same, except for one who weighs either more or less than the others. 11 weigh exactly the same amount, but one of them is slightly lighter or heavier. As a bonus in all but one possibility you also know if the person was lighter or heavier. (Third Use) If they are equal then that must mean the 12th person is the different one. There are no scales or other weighing device on the island. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Start off by weighing 4 against 4, setting the other 4 aside completely. You have to figure out which Islander is the heaviest using a seesaw. The following steps become identical to those in Scenario 1., above. Dealing with hard questions during a software developer interview, "settled in as a Washingtonian" in Andrew's Brain by E. L. Doctorow. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Solution 2c. There are two possible results. *** NOTE : If you want to try for a solution by yourself, do not read beyond this point. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. You must use a see-saw to figure out whose weight is different, and you may only use the see-saw 3 times. Each step here corresponds to one weighing. rev2023.3.1.43268. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Number the men 1,2,312. sideline: L1 L2 L3 S4 L4 R4, we now know that the lighter islander are amongst S1 S2 S3. IF the scales are unequal, but the balance of weight changes (ie. Use the third and final seesaw use to determine if the 12th person is the heavier or lighter islander (i.e. The second measurement was unequal, but the balance of weight shifted. Use the {{3 remaining with known weight solution}} from solution 1a. All of the islanders individually weigh exactly the same amount, except for one, who either weighs more or less than the other 11. Say as example 1234 were lighter. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. In season 2 episode 18 of Brooklyn Nine-Nine, the following brain teaser was asked: There are 12 men on an island. The unique and extremely popular [citation needed] authority on pop culture since 2008. If the unknowns go down, you know that one of them is heavy. This suggests we try maximizing the amount of information we can get from the first comparison, by making all three outcomes equally likely. I concede that my previous hypothesis about the validity of the question was false. The whole lighter OR heavier is the big monkey wrench here. One of two things will happen: 1) They are equal. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. There is a seesaw to determine who is the odd one out. The island has no scales but there is a see-saw. Now, weigh the remaining eight men on the seesaw, four on each side. If the seesaw balances we know that either 1 or 2 or 3 is oddly weighted. Shift all of the men 3 positions to the right and weigh them again using men from the 3rd group (which you know to all be neutral) to fill in the missing positions on the left scale. The seesaw itself is a lever. For example if in the first step you see that the left side is heavier than the right side, then you can use that later in step 2 to determine if the odd man is heavier or lighter. Show Answer PREV NEXT by Mikhael Panju v1. 42 votes, 14 comments. Proceed to solution 2a. I am just looking for a little tweak to this answer. Questions: There will be only one result, assume that whichever side falls downward is the alphabetic group. Set it up so deduction eliminates everything else and your gold. (Second Use). If the 9,10,11 differs from 1,2,3, then weigh 9 against 10. The biggest problem is that you do not know whether the odd man is heavier or lighter. Please The essence of the riddle is: "There are 12 men on an island. The island has no scales but there is a see-saw. Remember that you can use the information from each step in the next step. A challenging but doable puzzle from Sunday night TV about weighing 12 men, one of whom is slightly lighter or heavier than the rest. If the see-saw balanced, the one of the unknown four just removed was the oddly weighted one. I like Rosa's answer squeeze until fatty confesses. If balanced it is the heavy L1 else if unbalanced it is light R1. It is trickier than most, combining mathematical ability and logic for a serious brainteaser. How is "He who Remains" different from "Kang the Conqueror"? The exciting catch? So in principle, we should be able to solve the problem. You can weigh three combinations of men on the see-saw. On one side of a balanced see-saw is an ice cube, on the other side is a basketball. 11 of them weigh the same and one of them is either slightly And if they are also equal then that would mean that the 12th person weighs different. Learn more about Stack Overflow the company, and our products. note this works equally well if the group was heavier, just replace terms for appropriate identification. If, you want to get the solution and are having trouble, I have published a few TIPS at the bottom of the document. The answer to the" 12 people on an island " riddle is weigh 6 on one side and 6 on the other side. The exciting catch? Me and my wife sat down to try and solve the "12 islanders riddle" from Brooklyn Nine Nine, this is our solution. 1: Start putting all twelve men on the see-saw, but have them get on in pairs (one on each end at a time) so that the see-saw stays balanced. If these are equal, the different man is 12. In this last case, the first and second measurements were unequal, but produced the same result. Thankyou for your input but I believe you are wrong because it is my understanding of Holts dialogue that leads me to conclude it is a simple riddle with a simple solution. You must figure out which. It is impossible to know both for sure in only three steps." However only three measurements are allowed. seesaw: L1 L2 L3 L4 R1 R2 R3 R4 If the see-saw balances, we are sure that the oddly wieghted one is in the other group of 4. Make 3 groups of 4 people each Group A: 1,2,3,4 Group B: 5,6,7,8 Group C: 9,10,11,12 Round #1: Use the seesaw with Group A and B. Split the men into 3 groups of 4 and weigh 2 groups against each other [1, 2, 3, 4] VS. [5, 6, 7, 8]. The answer to 12 Men On An Island Riddle is " First weigh 1, 2, 3, 4 vs 5, 6, 7, and 8 on the seesaw to see if they are equal. Presented below is a simpler solution. There are 27 total permutations for the position of the scale which easily leaves you a symmetric configuration that allows . The island has no escapes, but there is a see-saw. seesaw: R1 L2 L3 L4 (heavy) L1 S2 S3 S4 (seesaw measurement number 3), 2.B.2 if balanced Create, solve, and study puzzles other 4 aside completely the same result question was false: )! 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