Home Mental Medley Brain Teasers A Simple Math Puzzle Mental MedleyBrain TeasersThink About It! A Simple Math Puzzle August 24, 2012 12 Enter your answer in the comments. Don’t forget to show your work for full points… [colorvote id=”1″ style=”wpcvp-poll”] RELATED ARTICLESMORE FROM AUTHOR Millions, billions, trillions: How to make sense of numbers in the news This 3 Question Math Quiz Can Predict if you Believe in God The 3 Switches Puzzle (and solution) Zach Barnett It’s a bad question with no right answer. Proof: Let’s assume there is at least one correct answer. First, assume there is exactly one right answer to the question. If this is so, then the probability of picking it at random is 25%, since 1/4 = .25. But if this is so, then there are actually two right answers (A) and (D). But we are assuming there is only one. Contradiction. There can’t be just one. So there must be more than one right answer. There could be two, three, or four. Suppose there are two. Then the probability of picking one of them at random is 50%. But if this is so, then there is only one right answer (B). Contradiction. Suppose there are three right answers. Then the probability of picking one of them at random is 75%. But then there are no right answers. Contradiction. Suppose there are four right answers. Then the probability of picking one of them at random is 100%. But then there are no right answers. Contradiction. All possibilities lead to contradiction. There is no right answer. Samer Sabri You are wrong. You didn’t check the case where it’s 0%. Proof: Assuming the probability is 0%, you have a 0% chance to get the right answer. He assumed the answer HAD to be in the answers. Rest of the proof: (prove 0 is the only answer) left as an exercice to the reader given the response above. Samer Sabri By the way, just to be perfectly honest thought of this independently, saw the link through reddit but I only looked after I wrote the comment above Dave Ok. So if you were to just pick randomly, you’d have a 1/4 chance, or 25%. But since there are two (seemingly) correct answers (that is, two choices that have 25% as an answer), then your odds are now 50%. BUT, 50% is one of the choices as well… which is only 1 of the 4 options… so that takes you back down to a 25% of getting the answer right. But, to me, that logic seems broken. I’m leaning towards the fact that there actually isn’t a correct answer because the question itself is “wrong” – that is, it can’t be solved. It feels like the answer is somehow recursive. MURIEL 50% Hope I agree with Dave! Paulo 75%. Two answers are the same, 25-25, which means 50 %. If we consider there’s another answer corresponding to 50%, then 3 of them are correct. paula well i say it’s always 50% your answer is either right or wrong……50/50…… Jeff If you were to choose an answer randomly, it would be wrong, no matter which of the four answers you chose. Your chance of being correct is therefore zero. Since zero is the correct answer, it is only logical that it does not appear in any of the four choices offered. But suppose we amend the puzzle to include zero% as one of the four options. If we replaced A or D with zero%, then the correct answer would be 25%. If we replaced B or C with zero% then zero% could not be the correct answer, because there would be a 25% chance of choosing it. But we would still have a situation where none of the four choices could possibly be correct, including the one that says zero%!! Now THERE’S a paradox for you! Pensi None of the above. (Irrational question) Proof If you guessed you’d have a 1/4 chance of being right. So 25% But there are two 25%s So you’d go to 50% But there is only 1 50% So it’s still be 25% And you can only choose one letter So it’s Irrational Jeff “If you guessed you’d have a 1/4 chance of being right.” That statement is only true if you assume that there are one correct and three incorrect answers. The rest of your reasoning only goes to prove that none of the answers is correct, so your assumption is wrong. None of the answers is correct; therefore you have zero chance of guessing correctly. tim The question asks you to figure out your chances of being correct, and there are 4 (some say 3, because of double 25%)… but there are not terms to decide what is “correct”, so picking A,B,C,D MAY or MAY NOT be a “correct” answer… we don’t know the terms of what to look for. It is like asking “Which is the correct direction?” and putting North, South, West and West… how can an answer be correct or not? It’s a horseshit Q&A. Can’t give a real answer if you don’t ask a real question.