![[Logic Quiz] Flexible Thinking and Creativity Are Key! From Classics to Tough Challenges, All in One Go](https://media.ragnet.co.jp/img/1200__png__https://www.ragnet.co.jp/files/2025/07/45697db22039adfb7ff602a03e2cb2a1.webp)
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!
- [Battle of Wits] Stimulate your intellectual curiosity! Quiz questions that get adults excited
- [Genius if you can solve it?] Insight and intuition: a challenging IQ quiz
- A quiz that seems easy but is actually hard: trick questions that make you think flexibly
- Genius if you can solve it? Super-difficult Quiz Collection
- Take on the challenge like a puzzle! A collection of logic quizzes that also work as brain teasers.
- [Interesting] A collection of brain teaser quiz questions. Let's train your brain!
- [Interesting] Collection of Math Quiz Problems
- Riddles for college students. Questions that test thinking and creativity.
- [Brain Training] Difficult Riddles That Even Adults Struggle With
- Fun quizzes for elementary school kids: a collection of questions everyone can enjoy together
- Also great for brain training! A flash of intuition is the key to solving these insight quizzes.
- Hard to get right on the first try! A quiz you’re guaranteed to get tripped up by.
- A math quiz for adults. Can you solve it?
[Logic Quiz] Flexible Thinking and Creativity Are Key! A One-Stop Introduction from Classics to Brain-Twisters (1–10)
There are 200 fish. 99% are guppies. How many fish need to be removed to make 98% guppies?
See the answer
100 animals
There are 200 fish in total. Of those, 99% are guppies, which means there are 198 guppies and 2 non-guppies. If you want to make the guppies 98%, you have to reduce the number of guppies. Since there are 2 non-guppies, if you reduce the guppies from 198 by 100, you’ll have 98 guppies and 2 other fish, making it 98%. Reduce by 100 just to lower it by 1%? It might be surprising, but that’s the interesting part of this problem.
Of the coins placed on the table, only 10 are heads up, and all the rest are tails up. While blindfolded, how can you divide the coins into two groups so that both groups have the same number of heads-up coins?
See the answer
Divide the coins into 10 random coins and the remaining coins, and flip all 10 coins over.
It doesn’t matter how many of the initial 10 coins are heads up. If n of the 10 coins are heads, then the remaining heads are 10−n. When you flip the 10 coins, the number of heads becomes 10−n, so both groups end up with the same number of heads: 10−n.
What is the largest number that can be made using the three digits 1, 2, and 3?
See the answer
3 to the 21st power
If it’s a three-digit number, 321 is the largest, but if it’s 3 to the 21st power, it becomes the larger number 10460353203.
There are two incense sticks that each burn out in one hour. How can you use them to measure 45 minutes?
See the answer
Light three points simultaneously: one stick at one end, the other stick at both ends. When the first stick burns out, light the remaining end of the other stick.
An incense stick lit at both ends should burn out in 30 minutes. If you light one end first, by the time it has 30 minutes of burn time remaining, lighting the other end will make it burn twice as fast, so 30 ÷ 2 = 15 minutes, and everything will burn out in a total of 45 minutes.
“There were two sunny days.” “There was only one cloudy day.” “There were two rainy days.” “No two consecutive days had the same weather.” “The day before a rainy day was not sunny.” Determine the correct weather for Monday through Friday.
See the answer
Rain → Sunny → Cloudy → Rain → Sunny
Because the day before the rain is cloudy, we know that the sequence includes “cloudy → rain.” The remaining days are two sunny days and one rainy day, and from the condition that the same weather does not occur consecutively, the order “rain → cloudy → rain → sunny → sunny” is derived.