15 fun tasks to train your mind and wits

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2024-01-13 00:26

Here are riddles from the collection "The Puzzler" by Nikolai and Pavel Poluektov. Test your wits!

Problem 1

In supermarkets, the canned fish section is piled high with sardines, but the fresh fish section never has them. How can this be explained?

Answer options

1. Sardines are inexpensive fish, it is more profitable for fishermen to roll it up in a jar right in the sea than to bother with deliveries of freshly caught product to stores.
2. Fresh sardines have an unpleasant smell and taste that only go away after conservation.
3. Sardines? They just don't exist!

Correct answer: 3

This fact is surprising to many, but you can vouch for its 100% reliability: there is no such kind of fish as sardines in nature. Sardines are small canned fish of a wide variety of breeds. It's like sprats (a direct analogy) and the mysterious surimi fish, which supposedly is part of all crab sticks: surimi means "minced meat" in Japanese;

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Problem 2

You are approaching a toll station on the highway. The checkpoint is organized traditionally: any cars can move along the right lane - cars, trucks, buses, otherwise only cars. Which row should you stand in?

Answer options

1. To the right, closer to the truckers!
2. Not to the right! Stay to the left!
3. It doesn't matter at all - the waiting time in the queue in each row is about the same.

Correct answer: 1

Lines in such places have a certain capacity for self-regulation - in the sense that everyone seeks to stand in a row of the shortest length. As a result, the lengths of all rows are really about the same - but not the waiting time!

The fact is that the waiting time is determined by the average time it takes one car to pass the checkpoint (open a window, pass a bill, take change and a check, drive through), multiplied by the number of cars in the queue.

If the length of the queue of cars and trucks is the same, then the cars in the “cargo” queue will be three to four times less than in the “passenger” - trucks, especially wagons, are several times longer than cars. This means that it will be possible to overcome this queue much faster!

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Problem 3

Three friends check into a hotel, a room costs $ 27, they drop $ 9, pay and go to check in. The receptionist checks the computer and finds out that guests have booked through booking.com, which means they are entitled to a $ 5 discount.

He hurries to them - to return the excess, on the way he realizes that 5 cannot be divided between three, and decides to give each of them a dollar, keep $ 2 for himself. Thus, each tourist gets a dollar back, and the number eventually costs them $ 8 × 3 = $ 24, another $ 2 was taken by the porter, in total this gives $ 26, but it was $ 27! How should this be understood ?!

Answer options

1. $ 2 should not be added, but subtracted.
2. It is generally impossible to count this way, because the amount contributed by the guests is counted twice.
3. The receptionist had to give $ 2 to each guest and keep $ 1 for himself, then everything converges - $ 3 × 2 - $ 1 = $ 5.

Correct answer: 1

The problem is remarkable in that it invariably confuses everyone, including people who once successfully solved it and even remember that "there is some very simple solution there."

So what are we adding up? Money actually paid by guests ($ 8 × 3 = $ 24) with money assigned to the receptionist ($ 2) and what do we expect to receive? After all, this $ 2 is already included in the amount paid by the guests! This sum contains everything: both the money received by the hotel and the "fee" of the porter.

Therefore, if we want to get something meaningful, then we can subtract the "fee" from $ 24 - we get an honest price for a room with a discount ($ 22), or add $ 3 - then we get the price for a room without a discount ($ 27).

Our sum ($ 24 + $ 2) is a nonsensical value "the cost of a discounted room plus double the receptionist's fee," and why should it suddenly coincide with the original cost of the room is absolutely incomprehensible.

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Problem 4

Ivan sold the car to Kirill for 1 million rubles. Cyril traveled for a month, realized that he did not like the car, and offered Ivan to buy it back. He agreed - but for 800,000 rubles. A month later, Alexei offered Ivan to sell the car to him, and they agreed on 900,000 rubles. Once the three of us met in a bar, the friends began to make fun of Ivan:

- Imagine, Lyosha, he earned 200,000 on me! - said Cyril.

- Yeah, and I have another 100, 300,000 in total! And this is on friends! Do you have a conscience, Wan?

How much did Ivan actually help out?

Answer options

1. 1, 1 million rubles.
2. 1, 2 million rubles.
3. 1.3 million rubles.

Correct answer: 1

Actually, Ivan did not earn anything on the buyback of the car from Kirill, but on the contrary, he spent 800,000 rubles. The next time he could sell a car at a lower price (cars generally tend to get cheaper over time), and then he would only lose.

He was lucky that Alexei was not very practical and did not bargain with a friend. So how much did Ivan help out in the end? 1 million rubles for the first time and another 100,000 rubles. (900,000 - 800,000) in the second, only 1.1 million rubles.

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Problem 5

- Gentlemen, this is Proshka, the local fool! Now I will show you a wonderful trick! - With these words, the mischievous gentleman held out both palms to the boy: in one there was a copper penny, in the other - a crumpled banknote worth one ruble. - What do you choose, Proshka?

Proshka grabbed the coin and, triumphantly, put it in his pocket. After that, the same trick was done with him three more times: the boy always chose a shiny coin and never a worn-out bill.

- I say - you fool! - repeated the gentleman, and the company, laughing, proceeded on.

What do you think - is Proshka a fool or not?

Answer options

1. Yes, judging by this story.
2. No.
3. Proshka may be a fool, but his producer is cunning.

Correct answer: 3

If Proshka had chosen a banknote at least once, then his whole "career", of course, would have ended there. It is unlikely that anyone would be amused if he showed such rational behavior, there is nothing unusual or funny about it. But, choosing a coin over and over again, he can count on the fact that the gentlemen will like the trick and they will want to see him again and again - then he will have a regular income, albeit low, but a regular one.

In the above story, he has already received 20 kopecks - to perform like that five more times, and the cherished ruble is in his pocket. Taking into account that selfish people are often incited to begging the unfortunate, it should be admitted that the one who taught Proshka to act in this way is undoubtedly a man of considerable cunning.

And even if Proshka himself came up with this, then the third answer is still correct - then it just turns out that Proshka is his own producer. It is not known whether he is smart or stupid, but he is certainly a cheat. And the fact that cunning and stupidity can easily be combined in one person is well known.

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Problem 6

One gentleman lived in a skyscraper on the 17th floor and had the following peculiarity: he always went down the elevator to the first floor, but when he returned, he would take the elevator up to the 14th, when until the 15th, and then he walked on foot. What's the matter here?

Answer options

1. Something is wrong with the elevator (the buttons were there, perhaps, the hooligans burned them?).
2. Something is wrong with the master.
3. Climbing two or three flights of stairs is a great exercise!

Correct answer: 2

Why doesn't he press the "17" button? Obviously, he either doesn’t want to, or he cannot. And rather the second - if he liked to climb on foot, then why would he leave himself only two or three flights? "Physical education", so seriously. Moreover, then it is not clear why he never descends on foot.

In general, apparently, it really cannot. The version about burnt buttons is also unsatisfactory - it does not explain why he rises to different floors, and not always to the 15th (if "16" and "17" are disabled) or always to the 14th (if the button is also broken "15"). In short, the lord is a midget, he can jump to the "14" button, if you're lucky - up to "15", higher - nothing.

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Problem 7

Pasha and Alyosha decided to buy a bun. But they do not have enough money: Pasha has a ruble, Alyosha has nine rubles.

- And come on, - says Pasha, - let's throw in one bun at least? Let's eat it in half.

Alyosha agrees, they fold and … still not enough. So how much did the bun cost?

Answer options

1. RUB 9
2. RUB 10
3. RUB 11

Correct answer: 1

If you started writing some equations, or rather, inequalities, then, of course, you can also act this way: you learned that a bun costs less than ten rubles, and thus came to the correct version.

But you can solve faster, by simple reasoning. If Pasha lacked only one ruble to buy a bun, and with the Alyoshans is still not enough, then this can only mean one thing: that Alyosha has no money at all. And if he lacks nine rubles to buy, it means that this is how much a loaf is worth.

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Problem 8

The teacher writes down the numbers on the blackboard - 13, 21, 34 - and asks the students to continue the sequence, adding at least two more subsequent numbers. They argued for a long time, eventually came up with three different options, but they are not sure of any of them. Which one will you choose?

Answer options

1. 42, 56.
2. 50, 69.
3. 55, 89.

Correct answer: 3

A question for erudition, if you do not know the answer, it will be very difficult to guess. It should be noted that 13 and 21 add up to exactly 34, and what sequence is expressed by the formula "Each subsequent is the sum of the previous two"? Quite right, this is a sequence of Fibonacci numbers: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, etc.

Curiously, the Fibonacci numbers by their author, Leonardo of Pisa (1170–1250; Fibonacci was nicknamed him only after his death), were proposed to count the number of rabbits known for their fertility in each generation.

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Problem 9

In Omsk, a competition for eating dumplings is held - who can master the most. Only those who are able to eat at least a hundred are allowed to the final. Four reached the final: Alexander, Boris, Vladimir and Gennady. It is known that Alexander won, Boris and Vladimir ate 599 dumplings for a couple, and in total, exactly 1,000 were destroyed in the final.

How much did the winner eat?

Answer options

1. 300 dumplings.
2. 301 dumplings.
3. 302 dumplings.

Correct answer: 2

For brevity, let's designate what each "athlete" eaten by the first letters of their names: A, B, C and D. We know that A + B + C + G = 1000, B + B = 599 (and, therefore, A + G = 401) and that A, B, C, D ≥ 100.

It follows that A ≤ 301, but then Alexander can be the winner only if Boris ate 300, and Vladimir 299 (or vice versa, which is completely unimportant to us - we are not interested in those who took second and third places; it is important that if someone- then he ate 301 or more of them, then Alexander cannot win in any way), Gennady ate exactly 100, and Alexander 301 dumplings. This is the answer.

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Problem 10

In Pereslavl-Zalessk from time immemorial there was a Blue Stone, which was worshiped by the Merians and other pagans. The monks of the nearby Borisoglebsk monastery dreamed of getting rid of the neighborhood with the stone and in the winter of 1788 they took him in a sleigh along Lake Pleshcheevo, but the ice cracked under the weight, and the stone went under the water to a depth of about 1.5 m. And 70 years later he took it and went out back to shore. How did he do it?

Answer options

1. It was carried out by the ice.
2. It was carried away by the algae growing underneath.
3. I got out myself, the stone is magic!

Correct answer: 1

As you know, water in a reservoir freezes from above. Thus, the surface ice has the ability to capture the stone. In spring, the ice cracks, and an ice floe with a stone ingrown into it can drift - in the direction where the wind blows on average. In Pereslavl, the prevailing direction of the wind is from the lake to the monastery, and the Blue Stone was carried there.

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Assignment 11

In the old days, in a storm, sailors poured oil or liquid fat (for example, whale fat) into the water. Why did they do it?

Answer options

1. Oil on the surface of the water interferes with the excitation of waves.
2. Silly superstition, sailors simply sacrificed to Neptune.
3. Nutritious food attracts a large number of fish, which break waves with irregular body movements.

Correct answer: 1

Waves in the water rise well if there are already waves there: the wind blows up the ripples, and the waves grow and grow. And if there are no ripples, then they will grow especially and not from anything. The oil film suppresses the appearance of ripples, this is the effect: the waves on the fat film are lower and weaker.

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Assignment 12

Can you shoot ice bullets?

Answer options

1. If not in a queue, then you can.
2. If you shoot very quickly - so that the bullets do not have time to melt.
3. No.

Correct answer: 1

Generally speaking, the answer depends on what you want. We will proceed from the assumption that the most common task is to hit the target. Then you will not be able to shoot in bursts: the ice will melt in the heated barrel, and at best, drops will reach the target. For the same reason, it will not be possible to shoot ice over long distances - it will melt in the atmosphere.

Note that the idea of ice bullets is a godsend for a detective writer, this is an ideal murder weapon - evidence disappears in a few minutes! Old Agatha would be pleased.

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Assignment 13

Why is it possible to fry a barbecue in the mountains, but it is almost impossible to cook a soup?

Answer options

1. It is so cold at altitude that it is not possible to heat the water above 30 ° C.
2. Despite the fact that the fire is as hot as in the valley, there is no way to heat the water up to 100 ° C.
3. Nonsense, it's not a problem to cook soup, the main thing is to take a saucepan with you.

Correct answer: 2

The lower the atmospheric pressure, the lower the boiling point. The higher the mountains, the lower the pressure - which means the lower the boiling point of water. The boiling point shifts by one degree with an increase in altitude by 300 m, so that in high mountains the water cannot be heated to more than 70 ° C. In such "boiling water" everything is cooked for a very, very long time, and even brewing tea is problematic for them.

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Assignment 14

In the igloo (an Eskimo house made of ice), fires are made for heating. In theory, this should lead to dampness - the ice melts, around the puddles, flows from the ceiling - but no, the igloo is always dry. What's the secret?

Answer options

1. Weak fire - if you make a fire harder, then the water will be full.
2. The emerging water, like a sponge, is absorbed by the ice.
3. Eskimos regularly wipe wet ice.

Correct answer: 2

As established by L. D. Landau and E. M. Lifshits (Soviet scientists), the melt (in our case, water) completely wets (which means it is effectively attracted; here mercury, to make it clear, does not wet anything) the solid phase of the same substance (i.e. ice).

And since ice is a rather porous substance, it manages to absorb all the water in the Eskimo dwelling. Of course, everything has its limits: if you put a heat gun there, sooner or later the walls of the igloo will flow, but the heat from the fire and human bodies is not enough to get the ice wet.

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Assignment 15

Marina Sergeevna bought a fashionable vacuum cleaner with a transparent body and a hose. Three days later, she came to the store to hand it back: they say, the product is defective, when working in the hose, there are some discharges. The store checked the device and made sure that it is completely serviceable. Who is deceiving whom?

Answer options

1. Nobody: sparks and the truth that is, then no.
2. Marina Sergeevna, she invented everything.
3. Store employee - I really don't want to take the marriage back.

Correct answer: 1

It is known that dielectric bodies are charged by friction against each other. When the vacuum cleaner is operating, dry dust rubs against the hoses; discharges visible to the naked eye can occur between charged particles. Why did Marina Sergeevna see this, but the shop assistant did not? The answer is obvious: Marina Sergeevna pumped dust into the vacuum cleaner, and the seller - clean air.

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Even more unusual problems for the knowledge of logic, mathematics and physics can be found in the book "Puzzle" by Nikolai and Pavel Poluektovs. It will appeal to those who are not afraid to test their ingenuity in practice.