[Logic Quiz] Flexible Thinking and Creativity Are Key! From Classics to Tough Challenges, All in One Go
Logic puzzles that call for flexible thinking and free imagination!
In this article, we introduce a wide range of problems—from classic ones you might see on TV or in magazines to challenging brainteasers with a twist.
Critical thinking and reading comprehension are certainly important, but surprisingly crucial is letting go of assumptions!
That “Isn’t this obviously what it means?” is often wrong to begin with.
Take this opportunity to clear your mind and tackle the problems without being bound by unconscious assumptions!
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[Logic Quiz] Flexible Thinking and Creativity Are Key! A One-Stop Introduction from Classics to Brain-Twisters (1–10)
There are pieces of paper labeled with the numbers 1, 2, and 3 placed face down. You can ask the questioner only one question, and the answer will be either “Yes,” “No,” or “I don’t know.” However, there is a question that allows you to determine the number. What is that question?
See the answer
If you add 0 or 1 to the numbers written on the paper, will the total become greater than 2?
If it’s 1, it won’t be greater than 2, so “No”; if it’s 2, it could be 2 or 3, so “Unknown”; if it’s 3, it will be greater, so the answer would be “Yes.”
I fell into a 30-meter-deep pit. You can climb 3 meters every hour, but immediately slip down 2 meters. How many hours will it take to escape?
See the answer
28 hours
It climbs 3−2=1 meter every hour. However, at the 27th hour it will be at the 27-meter mark, so if it then climbs 3 meters, it can escape without sliding down 1 meter. Therefore, the correct answer is 27+1=28 hours, not 30 hours!
One of three brothers secretly ate some sweets. The eldest said, “The second brother is the culprit.” The second said, “The youngest is the culprit.” The youngest said, “I’m not the culprit.” Only the one who secretly ate the sweets is lying. Who is the culprit?
See the answer
second son
If the eldest son is the culprit, then the second son must be lying, and if the third son is the culprit, then the eldest son must also be lying. This breaks the assumption that only the person who secretly ate the food is lying. If the second son is the culprit, then he is the one lying while the eldest and third sons are telling the truth. Therefore, the correct answer is the second son.
There are four boxes, and at least one of them contains treasure. Condition 1: If there is treasure in box A, then there is also treasure in box B. Condition 2: If there is no treasure in box C, then there is also none in box D. Condition 3: If there is none in box C, then there is also none in box B. If you can choose only one box, which box should you select to obtain the treasure?
See the answer
Box C
Let's focus on box C, which has the most information. If the treasure is not in C, then it is also not in B or D. However, if it’s not in B, then it’s not in A either. In other words, if it’s not in C, it’s in none of the boxes. Therefore, assuming the treasure is in exactly one box, the answer is C.
A ballpoint pen and an eraser together cost 110 yen. The ballpoint pen is 100 yen more expensive than the eraser. How much does the eraser cost?
See the answer
5 yen
Given that the eraser and the ballpoint pen together cost 110 yen, we have “eraser + (eraser + 100 yen) = 110,” which leads to “eraser = 5 yen.” It’s a question where people often mistakenly answer 10 yen, but if the eraser were 10 yen, the pen would be 110 yen, totaling 120 yen, right?