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Tomáš Macho
October 11, 2015, 9:05pm
Reading time: 6:01

14 Most Incredible Logic Riddles To Train Your Brain

Keep in mind that common sense often overrules the complicated problem-solving methods.

Tomáš Macho
October 11, 2015, 9:05pm
Reading time: 6:01
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14 Most Incredible Logic Riddles To Train Your Brain
Zdroj: Matthew Horwood / Getty Images
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You've probably already heard the saying that common sense is often more worthwhile than any unnecessarily complicated problem-solving methods that tend to create more problems at times. Well, this case isn't any different, so you better activate your common sense and your brain at the once. I highly doubt that mathematics was a popular subject for most of you, but I am sure that certain logical-mathematical tasks entertain even the minds of those who do not have much affinity for these sciences. For the greatest possible experience, try to come up with the right result before scrolling down for correct answers.


3 light bulbs

Let's start on a light note, with something that many of you probably have known for a long time. There are 2 rooms. In one, there are 3 identical switches, in the other, 3 identical light bulbs. Your task is to figure out which switch is for which light bulb, but you can only enter the other room once.

Source: Pictorial Parade / Getty Images

!SOLUTION: Turn on two light bulbs. After a while, turn one of them off again and proceed to use your only entrance to the next room. The pressed switch belongs to the lit bulb. The switch that has been switched off a moment ago will be connected to the light bulb that is off, but warm at the same, leaving only one left. Cold light would be a bit of a problem in this case.


Mysterious equation

Najzaujímavejšie logické hádanky, ktoré môžu dať vašej mysli poriadne zabrať

How come X has a different number at the end of the equation than at the beginning? Isn't that just an ordinary trick to throw you off? The answer is no. By all accounts, "zero point nine periodic" is actually equal to one. Under periodic, most people will imagine a long series of numbers that must end one day. However, this is not true, so the series of nines continues til' infinity. Arguably, one way or another, the difference of 0.00..1 remains. But since we have an infinite series of numbers, we can get "infinitely close" to the unit. Call it convergence, approaching a certain limit.




Alien abduction

Imagine an alien civilization attacking planet Earth and abducting a dozen people to an interplanetary station. To survive, they must get their brains busy. Ten abducted people stand in line, ranking from tallest to shortest. None of them are allowed to turn, so the last person in line sees everyones heads and the first one sees nobody. Each one gets a hat, either white or black. Subsequently, starting in order from from the tallest one, everyone shouts exactly one word, "black" or "white". A maximum of 1 error is allowed, so 9 out of 10 frightened Earthlings must guess the correct color. They have 5 minutes to discuss before putting on their hats. How will they solve the problem?



!SOLUTION: The only way out is to rely on an even / odd number. Unless a few victims are "slow" as someone in the comment section pointed out, all you gotta do is assign either an even or an odd number to a certain color. If the tallest person sees an even number of white hats in front of him, he shouts white. The chance that he guesses the color of his hat is 50%, but the aliens tolerate one mistake, therefore the real color of his hat is totally irrelevant. However, the person in front of him will already know whether an even or an odd number of whites are sitting on the remaining 9 heads, including him. So, if he sees an odd number of hats in front of him, it will be clear if the last white hat is on his head, or not. Thus the problem can be solved with any color ratio.




Lateral thinking puzzle

Dude lives on tenth floor. Every day on his way to work, he takes the elevator to the ground floor. On the way back from work, he takes the elevator again, but only to the seventh floor. From there, he takes the stairs and only goes directly to the tenth floor if someone else is coming along or when it's raining. Why?

Source: Dan Kitwood / Getty Images


!SOLUTION: The guy is a dwarf, so no matter how hard he tries, he can only reach the seventh button. If there's someone else in the elevator, he can ask them to press the tenth button, on a rainy day he presses the button with an umbrella. No need to look for something deep, these types of riddles only tend to activate lateral thinking.


Bertrand paradox

Imagine three boxes with two compartments like in the picture below. So, we have 2x3 bricks placed in separate "containers". Accidentally, you open one compartment. If you come across a gold brick, what are the chances that there will be a bright yellow piece of metal in the second part of the box again? Think carefully.


Najzaujímavejšie logické hádanky, ktoré môžu dať vašej mysli poriadne zabrať

!SOLUTION: How many of you answered 50%? Not the right answer, though. The chance that there'll be gold again in the second part of the box is 2/3. There are three bricks, and the fact that two of them are in the same double box does not mean that you cannot choose them at random. Thus, in only one case is it possible that there'll be silver instead of gold.


Najzaujímavejšie logické hádanky, ktoré môžu dať vašej mysli poriadne zabrať


Even vs. odd numbers

What is the ratio of all odd numbers to all even numbers?   

Najzaujímavejšie logické hádanky, ktoré môžu dať vašej mysli poriadne zabrať

 !SOLUTION: The answer half or 1:2 is not incorrect. In fact, the ratio is absolutely equal. How is it possible? Based on these three facts: Both are infinite. Each odd number has its next number, which is twice its value. In the same way, each even number has the other half, a.k.a. a number that's equal to half the value.


Sheikh's property

The rich sheikh on his deathbed called over his two sons. He told them that he would leave all of his property to that one, whose camel arrives in the city second. The brothers hung around the city for a few days until they met a wise old man. He whispered something to them, after which they both quickly jumped on their camels and rushed toward the city. What did he say?


Source: Francois Nel / Getty Images


!SOLUTION: The wise old man advised them to simply exchange their camels.



Imagine you are in a deserted place without any light source. You have 4 tablets of the same size. 2 are blue and 2 are red. Since you are sick, you need to get exactly one red and one blue, but you have no idea which color they are. If you eat more, you'll overdose and die. What to do?


Source: John Phillips / Getty Images


!SOLUTION: Actually, there are two solutions. The first is to will bite exactly half of each, which will guarantee that you have taken exactly one red and one blue. Another, a bit of an alchemist solution is to crush all medication and swallow half of the powder.



Rescue bridge

Imagine 4 people stuck on island full of zombies. The only rescue is to cross the suspension bridge. The wise old man calculated that the zombies would catch up with them in 17 minutes. The problem is that the crossing of the bridge is only possible for two people at a time. At the same time they only have one lantern available (without it, the crossing isn't impossible, but after dark?!). In 17 minutes, all 4 people must be on the other side. Person A crosses the bridge in 1 minute. Person B in 2 minutes. Person C in 5 minutes and the old man in 10. How can they make it in 17 minutes?



!SOLUTION: First, A + B pass (2 minutes), and A returns (3 minutes). Afterwards, C and D pass (13 minutes). B returns after A from the other side (15 minutes) and together they leave the dangerous island (17 minutes).



Few short ones to finish

1. I'm looking at a picture. I do not have any siblings. The father of the man in the photo is my father's son. Who is in the picture?

2. It is spring and you find a carrot in the garden, with two coals lying next to it. Why are they there?

3. What do you call a woman who doesn't have all her fingers on one hand?
4. How is it possible that I was 13 years old the day before yesterday and I will be turning 16 next year?

5. What mathematical symbol should we insert between the numbers 1 and 6 to get a number greater than one but also lower than 6?


Source: Michael Phillips / Getty Images


1. My son

2. Because no one has cleaned up the melted snowman yet

3. Totally normal. Would you want to have all of your fingers on your hand?

4. Because I was born on December 31st and I've made that claim on January 1st 

5. Decimal point


I hope that some of these riddles entertained you and maybe even made you sweat a little. If you know of some interesting ones yourself, feel free to share them in the comments.


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