How can I solve this logical question

Brain teasers in the application: 60 examples & solutions

Everyone knows them, some HR managers love them - and applicants fear or hate them: Brain teaser. Also as Brain teasers, guessing questions or Trick tasks known. Large companies such as Google - previously notorious for its numerous brain teasers in job interviews - are increasingly dispensing with the puzzles. Nevertheless, brain teasers still find their place in some recruitment tests in this country. This can be a nuisance for applicants. But it is not a cause for concern. Because with the right strategy you are Easy to solve brain teasers. Here we show you how ...

➠ Content: This is what awaits you

➠ Content: This is what awaits you

Don't be afraid of brain teasers in the job interview

So-called Brain teaser (English for Brain tickler) meet applicants in Job interviews as well as in Assessment center or recruitment test. This usually includes mathematical tasks, logic puzzles, guessing questions, trick tasks or trick questions (less often case studies and case studies).

With the so-called Trick tasks or trick questions you have to pay close attention. Here is the Solution particularly simple, but well hidden. The task itself is only there to fool you. A classic for this is: "How much earth is there in a hole measuring 2 x 4 x 1 meters?" The answer: none. Because in one hole there is nothing.

Many rightly ask: Why do companies even use such questions? Short answer: Because they are different from it Findings about

  • Problem solving skills
  • creativity
  • Comprehension
  • Thought patterns
  • and logical thinking

the applicants hope for. Whether brain teasers are the best solution for this is controversial. Nonetheless, applicants should focus on such Prepare logic puzzles and intelligence tests, because they just happen.

However, many brain teasers have a special feature: The a there is no correct answer. Sure, with some puzzle tasks there is a clearly defined result. For many other tasks, however, different results are possible. Here the journey is the goal, i.e. the one Solution and approach of the candidate (see box "Fermi questions").

So whether you are in an interview or at one Recruitment test be asked for it: Always try the brain teasers according to the following five steps to solve:

  1. Analyze calmly. At the beginning, take your time and carefully analyze the question and task. Don't let yourself be put under pressure either. If a solution is too obvious, it is usually wrong. So don't let yourself be led off the beaten track.
  2. Ask questions. Questions are also not a problem during a conversation. Feel free to ask if something is unclear to you.
  3. Summarize the situation. When you have grasped the situation, briefly summarize it in your own words. Then start the solution.
  4. Verbalize the solution. Speak your thoughts out loud and give the other person the opportunity to understand your approach.
  5. Justify the result. Finally, present your result. Crucial: explain how and why you came to this conclusion. Clarify your method and the solution again.

Do you know the Fermi questions?

The typical brain teasers in job interviews include so-called Fermi questions. These are - roughly speaking - impossible guesswork. Typical Fermi questions and brain teasers are, for example:

  • How heavy is Manhattan?
  • How many gardens are there in Germany?
  • How many sheets of paper are copied in a day in Germany?

You already notice: One right one There can be no answer to this - simply because nobody knows it. To a Correct or Not correct or a sample solution is possible with this one Fermi problem neither. Rather, it is about a logical derivation and quantitative estimate for a problem for which practically no data is available.

In order to be able to solve such questions in a job interview, you don't need much more than a certain general knowledge, common sense - and that Courage to think out loud.

The trick is to break the task down into smaller sub-tasks and thus find a plausible solution. What those present want to see is how systematically and analytically you approach a seemingly unsolvable problem. After all, you can use this ability in your job.

There is a nice example of this on Wikipedia. The question:

How many piano tuners are there in Chicago?

A possible solution would be like this ...

First the assumptions:

  • About three million people live in Chicago.
  • About two people in one household.
  • There could be a piano in every twentieth household that is regularly tuned.
  • Pianos are tuned about once a year.
  • It takes about two hours to tune a piano, including travel time.
  • A piano tuner works an 8-hour day, a 5-day week, and works 40 weeks a year.

Then the bill:
(3,000,000 inhabitants) / ((2 people per household) × (1 piano / 20 households) × (1 voices per piano and year)) = A piano has to be tuned 75,000 times per year in Chicago.

A piano tuner can do the following work:
(40 weeks per year) × (5 days per week) × (8 hours per day) / (2 hours per piano) = a piano tuner can tune 800 pianos per year.

The solution:
According to this, there should be around 100 piano tuners in Chicago.

More than 60 brain teasers and brain teasers PLUS solutions

The following Brain teaser are ideally suited to challenge your logical-analytical thinking skills and your creativity as well as to train your lateral thinker potential.

Some tests come (slightly modified) from the book of the same name "Brainteaser in the job interview". Quite a few of them were Candidates already asked in job interviews.

You can get to the solutions by clicking on the word and the link “Brainteaser solution” under the respective question.

But please try it yourself first, to warm up, with these brain teasers ...

Picture puzzles and logic tasks

(The respective solution follows immediately with the next picture. Simply click through with the orange arrows)


40 brain teaser examples from the job interview

  1. You have nine balls of the same size and appearance, as well as a pharmacist scale. One bullet is a little heavier than the other. How do you weigh them out? But you can only weigh twice!
    Brain teaser solution
  2. You are in a room with three light switches that lead to three light bulbs in the next room. However, these cannot be seen from their room. Find out which switch goes with which bulb. You may only enter the adjoining room once!
    Brain teaser solution
  3. You want to go to a party. There are two doors in front of you, each with a doorman. Only one door leads to the party. And one doorman always lies, the other always tells the truth. You can only ask one question. What do you ask?
    Brain teaser solution
  4. Three friends stay in a hotel and share a room. That costs 30 euros per night. So everyone pays 10 euros. Shortly afterwards, the hotelier remembers that the room costs only 25 euros and sends the bellboy to the guests with 5 euros. He thinks: 5 is not easy to divide by 3. He keeps 2 euros and gives one euro back to each of the friends. So the three of them paid 9 euros each, making a total of 27 euros. The page secretly pocketed 2 euros: 27 + 2 = 29. Where did the missing euro go?
    Brain teaser solution
  5. There are 200 bottles in Sir Blake's wine cellar, 99 percent of which are red wine. The rest is white wine. How many bottles does Sir Blake have to drink to reduce the proportion of red wine to 98 percent?
    Brain teaser solution
  6. What is the angle of the hour and minute hands on a clock at 3:15 p.m.?
    Brain teaser solution
  7. What day is tomorrow if the day before yesterday was the day after Monday?
    Brain teaser solution
  8. Lisa overslept and has to hurry because she has an important interview at 10 a.m. The light bulb in her bedroom is broken, it is pitch dark. Since Lisa is not very neat, her socks are individually in the laundry basket. She has 68 black and 32 white socks. How many socks does she have to pull out to have a pair of the same color?
    Brain teaser solution
  9. One and a half chickens lay one and a half eggs in one and a half days. How many eggs does a chicken lay in a day?
    Brain teaser solution
  10. The only child Jochen stands in front of a painting and says: "The father of the person pictured is my father's son." Who can be seen in the picture?
    Brain teaser solution
  11. You are sitting in the interview and there is a square glass of water in front of you. The HR manager asks you: “Is the glass half full or half empty?” You say: “Half full!” The HR manager replies: “This is not a personality test! Measure exactly! ”But you have neither a ruler, pens or other aids. What do you do?
    Brain teaser solution
  12. You have two boxes. One contains 50 red and the other 50 green balls. You can pull a ball out of one of the boxes with your eyes closed. If it's a red one, you win; if you get a green one, lost. Before that, however, you can distribute the balls anywhere on the boxes to increase your chances. What do you do?
    Brain teaser solution
  13. What's next: Z - A - Y - B - X - C -?
    Brain teaser solution
  14. Daniel and Isabell invite three couples to dinner. Some people shake hands in greeting. Later, out of curiosity, Daniel asks who shook hands how many times. Although no one has shaken hands with their own partner or shook hands with the same person multiple times, everyone gives a different number. How many guests did Isabell shake hands with?
    Brain teaser solution
  15. A woman has two hourglasses. One runs for five minutes, the other for seven. But she wants to stop 13 minutes. What must she do?
    Brain teaser solution
  16. The digits from 1 to 9 have been put in a completely new order, it is:
    8 3 1 5 9 6 7 4 2. What is the organizational principle behind this?
    Brain teaser solution
  17. What is the next letter: J F M A M?
    Brain teaser solution
  18. You have three canisters: a full one with eight liters and two empty ones with a capacity of 5 liters or 3 liters each. You should measure exactly 4 liters. How do you do that
    Brain teaser solution
  19. What is more powerful than God, even more evil than the devil; the poor have it, the rich need it, and whoever eats it dies from it?
    Brain teaser solution
  20. You drive your car on a lonely country road on a freezing cold, dangerously stormy night. As you pass a bus stop, you see three people there: a) an old lady who is apparently near death and has to go to the hospital; b) an old friend who once saved your life; c) Your dream partner that you've been looking for all your life. The dilemma: you can only take one person with you. Who do you offer the space in your car to?
    Brain teaser solution
  21. You are in a rowboat on a small pond and have dropped anchor. When you catch up with him - does the water level rise or fall or does it even stay the same?
    Brain teaser solution
  22. You are in the interview. The HR manager offers you a game: starting with the number 10, you both add a number from 1 to 10 alternately. If you add up to 100 at the end, you win the game. It starts with 2 - so 10 + 2 = 12. It's your turn. But can you even win the game?
    Brain teaser solution
  23. What's next: 1 - 4 - 10 - 22 - 46 -?
    Brain teaser solution
  24. Two friends want to cross the river at a particularly deep and wide point. There is a boat on the bank, but only one person can carry it. Both cross the river anyway and move on happily. How do you do that?
    Brain teaser solution
  25. It is the day you start work. But there are two company entrances. One leads back outside, the other into the company. There is a guard in front of every gate - one always tells the truth, the other always lies. Both know the right door. You can only ask one guard and ask them only once. What's the question?
    Brain teaser solution
  26. A hotel guest comes into the restaurant in the morning and orders a breakfast egg. It should be cooked for exactly nine minutes. Unfortunately, the chef only has two hourglasses with which he can measure the time. One takes four minutes for the sand to run through, the other seven minutes. What does the cook do to still serve the guest a 9-minute egg?
    Brain teaser solution
  27. The mother is 21 years older than her daughter. And in six years she will be five times her daughter's age. But where is the father right now?
    Brain teaser solution
  28. The car pool consists of four people. One day the four of them have an accident. Three are seriously injured and require immediate surgery. Fortunately, the only uninjured one is a surgeon. However, he only has two pairs of latex gloves in his emergency kit and no disinfectant. How can he still operate on all three under sterile conditions?
    Brain teaser solution
  29. A well-known horse breeder leaves 17 horses to his three sons Jim, Jack and John. However, with one condition: Jim should get half of the inheritance, Jack a third and John a ninth. You are not allowed to kill an animal or dispute over the inheritance. The brothers are desperate until a cowboy rides up and helps them. How?
    Brain teaser solution
  30. Bill and Bob are dead on the floor of the room. A gusty wind is blowing through the open window. There are broken glass lying next to the corpses on the wet carpet. What happened?
    Brain teaser solution
  31. You have a cucumber that weighs 1200 grams. Their water content is 99 percent. How much does the cucumber weigh when the water content drops to 98 percent?
    Brain teaser solution
  32. The puzzle supposedly came from Albert Einstein, who said only 2 percent of the world's population could solve it. It goes like this: There are five houses, each with a different color. A person of a different nationality lives in each house. Everyone in the house prefers a certain drink, smokes a certain brand of cigarettes, and has a certain pet. None of the five people drinks the same drink, smokes the same brand of cigarettes, or keeps the same animal as one of their neighbors. The clues are as follows: The owner of the yellow house smokes Dunhill. The man who lives in the middle house is drinking milk. The Brit lives in the red house. The man who keeps a horse lives next to the man who smokes Dunhill. The Norwegian lives in the first house. The green house is to the left of the white house. The camel smoker likes to drink beer. The Marlboro smoker lives next to the one who has a cat. The Dane likes to drink tea. The Norwegian lives next to the blue house. The Marlboro smoker has a neighbor who drinks water. The German smokes West. The owner of the green house is drinking coffee. The Swede has a dog. The person who smokes Gauloise is holding a bird. Who has the fish?
    Brain teaser solution
  33. You know the graduation of the euro coins: 1 cent, 2 cents, 5 cents, 10 cents, 20 cents, 50 cents, 1 euro and 2 euro pieces are available. For example, suppose your wallet is very small and you want to carry the smallest amount of cash with you. Still, you want to be able to pay every cent - including one euro - exactly. What coins do you have to insert at least for this?
    Brain teaser solution
  34. You have two candles in front of you that you know will both burn for exactly one hour each. You should now measure exactly a quarter of an hour with these two candles. There is one problem, however: the two candles are made from different types of wax and don't burn evenly. If one is half burnt down, you cannot assume that exactly half an hour has passed. How do you manage to measure the quarter of an hour anyway?
    Brain teaser solution
  35. Early in the morning a man leaves his house drunk with sleep. First he goes one kilometer to the south, then four kilometers to the west. Then he is suddenly awake: a huge bear is standing in front of him. The man reacts instinctively and runs north as fast as he can. After exactly one kilometer, he arrives at his safe house. Oh, what color is the bear?
    Brain teaser solution
  36. You stand in front of a river and have to bring a goat, a wolf and a fern to the other bank. A rowing boat is available for this. But it is so small that you can only take one of the three - goat, wolf or fern - with you per trip.If you leave the goat alone with the wolf, the wolf will be happy about the delicious meal and will eat the goat. If you leave the goat alone with the fern, it becomes a snack. How do you manage to get the trio to the other bank without the goat or fern being eaten?
    Brain teaser solution
  37. Now there are two questions: In front of you is a die on the table that shows the number five. Question 1: What number do you see if you tilt the cube forward twice? And question 2: The dice shows the number four this time. You tip it forward once. Which numbers could the dice show now?
    Brain teaser solution
  38. Your colleague tells you an incredible story: he turned 32 on his last birthday. But next year he will be 36! The man is not crazy, by the way. When is your colleague's birthday?
    Brain teaser solution
  39. Mr. P. started in the department two weeks ago and is nervous in the first conversation with his new boss, because he loves logic puzzles. And in fact he starts right away: “I bet you that I can ask you a question to which you know the correct answer - only“ yes ”or“ no ”- but cannot tell me what it is ! ”Mr P. thinks for a moment and makes the bet. The boss then asks his question and Mr P. has to admit that he has lost. What question did the boss ask?
    Brain teaser solution
  40. Martina has borrowed a book from her colleague. She returns it on Monday. On Thursday, however, she spoke to her colleagues again about the book. She claims that she forgot a 50 euro note between pages 59 and 60 and is asking her colleague to return it. He doesn't even bother to look and accuses Martina of lying. Why can the colleague be so sure about this?
    Brain teaser solution

Brain teaser examples: 13 matchstick puzzle tasks

You may remember the following tasks from your childhood: Matchstick puzzle. Various figures or math problems are placed with matches, which have to be transformed into a new pattern or a coherent equation with just a few simple steps and changes.

That often sounds easier than it is. Sometimes spatial imagination is also required. The matchstick games selected here are among the trickier of their kind. Just give it a try. The respective Solution immediately follows the picture - just click through with the orange arrows ...


The illustration shows a giraffe looking to the right. At least with a lot of imagination. Place them just a match so that the giraffe looks to the left.

The trick is not to flip the giraffe horizontally, but to "rotate" it. You could also say: The giraffe is now lying on its backside and looking up.

Now it's time to do the math: The following equation is true. Still: lay down just a match um, so that the calculation still works out (the unequal sign is forbidden!).

Two solutions are even possible here. One of them: 3 + 3 = 6. Make a 3 out of 9 and a plus out of the minus (by the way, a second solution would be: 8 - 3 = 5).

The following equation is incorrect. 1 + 2 = 8 is mathematical nonsense. Place them just a match to make it right again!

The solution is easy to overlook: If you take a match from the 8, it becomes a 9 and if you place it above the 1, it becomes the 7th. It's right again: 7 + 2 = 9.

The equation shown does not work either. With the flip of just a match but if the calculation were correct again ...

Once you have understood the principle, it's easy: In this case, the 9 becomes a 3, the now free match turns the zero into an 8. Result: 8 - 3 = 5. That's right.

The following equation is incorrect. By killing it of a single match however, you can ensure a mathematically correct calculation. How do you do that?

Remove the match from the number six and place it over the minus sign so that it becomes a plus sign. The equation then reads: 3 + 2 = 5 and is correct again.

The figure shows 4 squares of equal size. Position 4 matches so that in the end there are only 3 squares of the same size.

If you think in the given form here, you will not find the solution. The trick is to add the third square above (or below) ...

This time there are only 3 squares of the same size. Put this time just two matches so that you end up with 2 squares.

With this puzzle, too, it is important to think in different dimensions. Who says that in the end both squares have to be the same size? Just…

You have 5 squares in a row. Now you can Move 6 matches. However, you should end up with 4 squares.

The trick is to think multi-dimensionally: If you free yourself from the template, you will find a solution with 4 squares of different sizes:

You will see the number 100 in front of you. Move it just two matches so that at the end there is the word "cat"!

This character is tricky. While the 100 can be read horizontally, the word "CAT" is there rotated 90 degrees to the right - and then also vertically:

Here the Romans calculated wrongly. Help him by just a match shift so that the equation works again.

In Roman numerals there is 7 = 1. With point and line calculations you get no further in this case. What helps is differential calculus: The square root of 1 is also 1 ...

Again the bill is wrong. Again you may just a match shift so the equation is correct.

XI + I = X - in German: 11 + 1 = 10 - that doesn't work. But: 9 + 1 = 10 - that's true. Fortunately for the Roman numerals, 9 is represented as IX:

In front of you is a farmhouse that is to be completely rebuilt. So far the portal points to the right, later it should look to the left - but you are allowed to do so just two matches knock down.

If you see the solution in front of you, you immediately say: "Of course, how easy!" In order to get there, however, you need above all perspective and spatial imagination:

The overturned sail mast should become two equal-sized squares. However, you are allowed to just two matches move. Which and how?

The riddle is not for people who only think in horizontal figures. The task was not to form squares, but rectangles - they can also be crooked.

What other readers have read

[Photo credit: Roman Samborskyi by Shutterstock.com]

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October 25, 2020Author: Jochen Mai

Jochen Mai is the founder and editor-in-chief of the career bible. The author of several books lectures at the TH Köln and is a sought-after keynote speaker, coach and consultant.

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