Paul Sloan - entertaining puzzles for lateral thinking

A journalist from Singapore posted on his page in social network a puzzle that he said was meant for 10-year-olds. A few days later, this puzzle blew up the Internet community and heated debate erupted in the comments. However, even the TV presenter himself did not know right decision when he posted this assignment, his friend's niece told him about it. The journalist quarreled with his wife over this puzzle.

After his post became very popular, he was contacted by experts from the SASMO organization and was told that the puzzle was actually for children from 14 years old.

Don't be discouraged if you can't come up with a solution right away, as this assignment is worth thinking about.

Develop your brain every day playfully with the whole family with

• Puzzle:

Two friends recently met a girl. They really want to know what day she was born. The girl named 10 dates, one of which could theoretically be her birthday: September 15, September 16, September 19, October 17, October 18, November 14, November 16, December 14, December 15 and December 17. Then she told one of them (A) the correct month, and the other (B) the date.

“I have no idea what day she was born, but I’m sure B was too,” A says after that.

“Initially, I didn’t know which day was right, but now I’m 100% sure,” B answered him.

“I know the correct date for sure, after phrase B,” A ended the conversation.

When does a girl celebrate her birthday?

Logic task about a pet store

Stepan Alekseevich recently acquired a store and decided to dedicate it to the sale of animals. He started with decorative dogs, because he already had them. Stepan Alekseevich bought spacious enclosures for them. If he lets one dog into each enclosure, then one will be left without a house. And if he places two dogs in each enclosure, then one enclosure will be empty. How many enclosures did Stepan Alekseevich buy, and how many dogs did he have?

Task "Two flocks" - develop logical thinking

Two packs of wolves live in the forest: the truthful - they never lie - and the liars who never tell the truth. Once a traveler stumbled upon a wolf and, when he found out that he was from a truthful pack, he asked to be led to the edge of the forest in order to get out of it. When they went further together, they met another wolf, and the guide wolf, at the request of the traveler, ran to find out which pack the second wolf belongs to. When he returned, he said that the wolf claims to be in the truthful pack. Question: what pack does the wolf that accompanied the traveler belong to?

Logic puzzle about a broken vase

Nine children were left without parental supervision in one room. When an adult entered the room and saw that from a vase self made only fragments remained on the floor, he began to ask everyone about who the culprit was. The answers were:

Masha: It's all Roller!

Pasha: Not true.

Alina: I did it.

Katya: Either Alina or Natasha broke it.

Roller: Pasha is lying.

Sasha: Alina did it.

Nastya: No, this is not Alina.

Natasha: Neither I nor Alina broke the vase.

Andrey: Natasha is right, but Valik didn't do that either.

Of all the replicas, only three are true. Who broke the vase in this scenario?

Football mindfulness task

In the football championship, where each team fought each other once, 4 teams participated: Alpha, Beta, Omega and Gamma. A team was awarded zero points for a loss, two points for a win, and one point for a draw. The final match ended: Alpha lost to Omega. But Alpha still won the games, while Omega did not improve their team's score. How did the Omega and Gamma teams play against each other?

Logic task "Three sisters"

Three sisters, Anastasia, Ekaterina and Anna, teach various items at colleges in New York, Berlin and Amsterdam. Anastasia does not work in New York, and Ekaterina does not work in Berlin. The one who lives in New York does not teach English language. The one who works in Berlin teaches higher mathematics. Ekaterina does not teach psychology. What discipline does Anna teach, and at the college of which city?

A number of words - eliminate unnecessary

Flounder, trout, dolphin, shark, stingray.

What is the missing word in this line?

Logic problem about sons

Ivanov and Kotov each have 2 sons who are younger than nine. Their names are Andrei, Vitalik, Lesha and Vasya. Andrei is three years younger than his brother. Vitalik is older than all the boys. Lesha is two times younger than the youngest Ivanov. Vasya is 5 years older than the youngest Kotov. 5 years ago, the difference in the sum of the years of the children of the Ivanovs and the Kotovs was equal to the sum today.

Match the names of the boys and their ages.

Logic task about elections

Six people - let it be 1, 2, 3, 4, 5 and 6 - are running for president, deputy and secretary of the "Magic Kingdom". However, it is not easy to distribute roles for them.

• 1 does not want to dominate.
• If 5 is not the president, then 2 does not want to be in charge, because then it will be necessary to dominate 3. 2 will not cooperate with 6 in any case.
• 3 will not work in the company if there are 5 and 6 in the bosses together. 3 will resign if 6 is the president or 2 is the secretary.
• 4 does not work with 3 or 5, because it does not want to be subordinate to one or the other.
• 5 does not want to be deputy president. But he does not want to take the post of secretary if the boss is 4. Plus, 5 will not work with 1 if 6 does not take one of the leadership positions.
• 6 will cooperate only if he is the President, or 3.

Everyone thought about who to put in the leading positions of the Magic Kingdom, but after thinking logically, they nevertheless satisfied the needs of each candidate.

How did they assign roles to all candidates?

All logic tasks with answers, so you can find out the solution using the button below.

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An interesting task - "Who?"

The editorial office employs the editor-in-chief, proofreader, layout designer, deputy editor and an ordinary journalist.

Their names are Kovaleva, Krichkovskaya, Ivanchenko, Hoe and Tyulka.

When the proofreader and the journalist studied at linguistic university They rented an apartment together. Chief Editor on the this moment not a family man. Tyulka and Kovaleva are enemies. Ivanchenko's husband was very happy when he found out that the editor-in-chief had allowed his wife to take another vacation in August. Hoe was upset when he learned from the editor-in-chief that the layout designer and proofreader would soon get married. Kovaleva and Krichkovskaya are not yet married.

Question: What is the last name of each editorial staff member?

Logic tasks are perhaps the most effective tool for developing logic and thinking in both children and adults.

Solving a logic problem involves a complex thought process. This is the consistent performance of certain logical actions, work with concepts, the use of various logical constructions, the construction of a chain of precise reasoning with correct intermediate and final conclusions.

Unlike most mathematical and other types of problems, when solving logical problems, the key is not to find the quantitative characteristics of an object, but to determine and analyze the relationships between all objects of the problem.

Take a holistic approach

Among the whole variety of logical tasks, children often choose a couple of their favorite categories and immerse themselves in solving them. is that enough?

Surely most of us at least once passed tests for the level of logic. Most of them are made up of some syllogisms or trick questions. We do not offer such tests, because we know for sure that it is impossible to determine the level of development of logical thinking with the help of a dozen or two questions, even approximately. As well as develop out-of-the-box thinking, solving only individual types logical tasks.

Classical logical, combinatorial and truth problems, regularities and mathematical puzzles, problems about figures in space and sweeps, for permutations and movement, for weighing and pouring; solved from the end, with the help of tables, segments, graphs or Euler circles - this is far from the whole variety of logical tasks, in the solution of which all kinds of mental operations are activated and creative, non-standard thinking develops.

Logic is a yummy for the mind

This is exactly what the students wrote on the blackboard before the start of one of the classes in our logic circle. What is the beauty of logical problems?

• they will be equally interesting for children who are passionate about mathematics and for “humanists”;
• many of them do not require knowledge of the school curriculum;
• even a preschooler without reading skills can solve them (for example, sudoku, rebuses, matchstick puzzles, gears and other tasks in pictures).

Children love to solve logical problems and riddles. They are interested! When I worked at school, I saw that the guys cope with the program, mechanically remembering the way to solve certain typical problems.

And tasks with asterisks immediately enlivened the class, both strong and weak students were included in the discussion process. At home, the children already could and wanted to explain this task to their parents. But even these problems with asterisks were located on the pages of the textbook in a random way, no system was developed.

Bitno Galina Mikhailovna

head teacher of LogicLike, teacher of the highest category

Only a systematic and integrated approach creates favorable conditions for the formation of non-standard thinking. "Food for thought" should also be balanced and varied. Try it yourself and invite your children to solve just such a selection of problems. This will help identify those links in the logic that need to be worked harder.

Try it yourself

In the online platform Logiclike, created to develop logic and mathematical abilities in children aged 5-12, the authors tried to implement everything that is often so lacking for both students and teachers in school programs. Consistency, involvement, interactivity, visibility, motivation ... But first of all, it is food for the mind, the very “yummy” that makes the child think, reason, test his strength, show creativity and rejoice when you manage to find the right solution.

• If you want to develop non-standard thinking and flexible logic in a child, give him a good exercise for the mind in the form of a variety of logical tasks, for which you need to use different logical laws and solution methods (method from the end, tabular method, using graphs or Euler circles, etc.). e.)
• Approach learning systematically: from theory to tasks, from simple to complex, from getting to know new types of tasks to reflection.
• Consider the specifics of thinking in children of primary school age - use visual images and visual materials.
• It is important not to impose a solution method on children, but to try to analyze it so that they themselves, through logical reasoning, find the correct answer.
• Introduce game elements into the learning process, use the learning capabilities of IT.
• Logic classes, like sports training, need regularity and a gradual increase in the complexity of tasks.

Work with your child and have fun!

The main objective of the course on entrepreneurship and innovation by Tina Seelig, Stanford professor and author of the novelty"Make yourself ", - to show students that for any problem you need to look for a creative solution.

To do this, she offers her students several exercises that you can use.

Exercise 1. The best of the worst

The group is divided into small teams, each of which must come up with the best and worst idea for solving the problem. When they are done, the teams write down each of their ideas on a sheet of paper. separate sheet papers: one of them says "BEST" and the other says "WORSE". Then defiantly destroy the sheets with BEST ideas and each team gets a piece of paper with the other team's WORST ideas. After that, they are given the task of turning this idea into a beautiful one.

Result

After looking closely at new ideas, participants usually realize that they are not so bad. For example, a group that got the idea to sell a bikini in Antarctica came up with the slogan "Bikini or death." Them new idea was to send people who want to get in shape on a trip to Antarctica. By the end of the hard journey, they could fit into a smaller bikini.

The group, which needed to perfect the idea of ​​cockroach sushi, put forward a proposal to open a restaurant called Cucaracha for an audience inclined towards gastronomic adventures, which would serve different kinds exotic sushi made with unconventional yet nutritious ingredients.

This exercise is a great opportunity to open your mind to problem solving. It shows that most ideas that may seem silly at first often contain an interesting grain. It helps to challenge assumptions that ideas are inherently good or bad and shows that with the right state of mind, you can find something of value in any idea or situation.

Exercise 2. Circus upside down

Write down all the stereotypes about a traditional circus: a big tent, animals, cheap tickets, touts selling souvenirs, multiple arena activities going on at the same time, loud and upbeat music, clowns, popcorn, strong men, fire eaters, etc.

Next, imagine the antipode of each of the described features. For example, the new list might include a low roof, no animals, expensive tickets, no barkers, sophisticated music, no clowns or popcorn.

Result

Once you've done the circus exercise, you'll find it much easier to think about changes in other industries: fast food restaurants, hotels, airlines, sports facilities, educational institutions and even in courts and municipal institutions.

When in the 1980s all circus shows were terribly predictable and secondary, with ever-decreasing audience numbers, the idea of ​​Cirque du Soleil challenged every preconceived notion of what a circus should look like.

Exercise 3. We take out wallets

Participants are asked to take out their wallets. They then pair up and talk to each other about their wallets. They discuss what they love or hate about them, or talk about how they are used for shopping and storing documents.

Result

Most people who use wallets are frustrated to some degree by the limitations of the item. Therefore, after the interview is completed, each of the participants begins to create new design wallet for your interlocutor - "client". The designer has only simple items at his disposal: paper, adhesive tape, markers, scissors, paper clips and the like. Customers love the new concepts and often say that if such a wallet was on sale, they would definitely buy it.

This exercise allows you to learn a lot of lessons. First, the wallet is a symbol of the fact that problems can be found everywhere, even in your own pocket.

Secondly, only a small effort may be required to solve these problems. People are usually happy to tell you about their problems.

Thirdly, simple solutions can be found with simple experiments. They do not require a significant amount of work, resources or time. And even if you fail, your costs are minimal. And all you need is just to start over.

Exercise 4. Drive over competition

AT business environment drive is always more important than competition. In order to confirm this thesis, Tina Seelig developed a special exercise.

Six teams receive five completed puzzles of 100 pieces each. Participants are given a minute to look at the finished pictures, after which the elements of all the puzzles are added together into one huge pile and mixed.

Then all the pieces are distributed among the six teams. In addition, each team receives 20 poker chips that can be used as currency. Teams must complete the puzzle in one hour.

Since the number of puzzles is less than the number of teams, the participants must decide whether they will compete, cooperate, or combine both strategies to complete the required pieces.

Result

To be successful, teams must work together. Since they know that the number of puzzles is less than the number of teams, at least one team must decide not to solve the puzzle but play some other role. Sometimes two or three teams merge. Sometimes a team may take on the role of a broker, exchanging pieces of the puzzle with other teams. Sometimes all the teams merged into one and worked together to solve the puzzle. The worst result occurs when all teams decide to compete against each other.

This exercise makes participants realize that in a resource-limited environment, motivating yourself and others to succeed is often a more productive strategy than pure competition. People who manage to tune in to this wave are able to actively take on board the skills and tools that others bring to the process, as well as rejoice at the success of others.

For more Stanford secrets, see Tina Seelig's book.

Product designer at Foursquare recommendation service John Steinback posted a note on his blog on Medium, in which he talked about how company employees develop their creativity and what exercises they use to do this.

The editors of the site publish a list of "creative exercises" that Steinbeck recommends.

Every Friday PX Team (Product Experience - ed.) The Foursquare service gets together and "exercise creativity" - performs special team tasks that help employees show their creative side. PX includes UX specialists, visual designers, copywriters, research and analysis departments of the company.

According to the author of the material, such meetings raise the spirit of the team and help each participant develop creativity in themselves. They allow PX employees to look at the problem through the eyes of their colleagues. In addition, they help build relationships between employees of different departments.

Every week the meeting is led by employees from different departments. The team, Steinback writes, is quite large, so the results of completing tasks are very different for everyone. Approximately half of the time allotted for the meeting, the employees solve the problem set by one of the colleagues, and then exchange the results and their thoughts.

John Steinback has put together a list of some of the exercises that Foursquare employees have been doing at Friday meetings over the past two years. The author believes that they will be useful to employees of other companies.

Create your own sandwich

The essence of the exercise is to come up with a sandwich that would reflect the personality of a specialist. The photos below show examples of work created by the Foursquare team.

"Blind" portraits

Participants are divided into pairs, and each employee tries to draw a portrait of his partner in five minutes without looking at the paper.

New "interface" of the office object

An exercise about which FastCompany wrote a separate article. Each employee who took part in the meeting received a picture of some office object - for example, an urn or a ping-pong table. The employee was required to come up with a new "interface" for the object - to think about how office workers could interact with him.

So, a bin, for example, could be angry at an employee when he does not throw out the garbage:

Watch face design for smart watch

The team was tasked with inventing new way display information on the watch face. “We were way ahead of our time,” says Steinbeck.

Matt maneuver

Employees must place some object in the center of a piece of paper. It is best if it will be something that the employee likes to draw, or that meets his vital interests. In the photo below - a couple of employees who chose headphones as such an item.

After that, four words or qualities are placed in different corners of the sheet. The employees in the photo chose adjectives such as "cheap", "expensive", "random" and "predictable".

Now the workers can begin to perform the task itself. Its essence is to gradually "move" the selected object in the direction of each quality - and redraw it in accordance with its position on the sheet. For example, the closer "headphones" are to the word "expensive", the "more expensive" they should look.

"Murder Mystery"

Using cards from board game Cards Against Humanity (they list various phrases, names famous people and so on), the employees had to explain how the "mysterious murder" was committed, and explain whether the suspect was guilty of it. The participants were required to use in their story all the words that fell out to them:

Flipbooks from stickers

This task was to create a “flipbook” (a small book with “moving” pictures when flipping through) with your own hands from ordinary office stickers.

Movie title puns

Each employee chose a famous painting, changed one letter in its title, and drew a scene from the new film. For example, the Quentin Tarantino film "Reservoir Dogs" was turned into "Reservoir Logs" by workers:

"One day of life"

Each participant in the meeting received the name of someone from the Foursquare team, as well as four various places. The employee was required to describe one day in the life of the person that he got, so that during this day the hero had time to visit all four designated places. The story had to be drawn in the form of a small comic strip.

"Emoji Song"

Employees were divided into pairs, together they chose some famous song and wrote down its lyrics using emoji. After that, other participants tried to guess what song is represented in each sequence of symbols.

"Mountain Paradise"

Each participant of the meeting had to draw a mountain, and on its top - a place where he would feel completely happy.

Comics featuring Swarm stickers

Employees who took part in the meeting each received a sticker from the Swarm app (the service that introduced the check-in feature after Foursquare). Each of the employees was asked to come up with a comic strip with the sticker that fell out to him, which would describe the history of his appearance.

Soundscapes

Employees were to be divided into groups of three. For each group, a video was prepared demonstrating the functionality mobile application Foursquare. The participants were required to come up with an unusual soundtrack for their video.

"Guess the celebrity by her preferences"

To complete this task, each employee had to choose a celebrity or public figure, and then collect ten "preferences" for her, which are available to Foursquare users.

"Collectible Cards"

The names of all those present at the meeting are folded into a hat or other container. After that, each employee draws a card with a name - and draws playing card representing the hero:

Create your own ads for Foursquare

In early 2015, Foursquare launched its first large-scale offline advertising campaign. The posters show people using Foursquare. Next to them are "bubbles" with words and expressions that describe their tastes:

When completing a task, each employee received a photo of one of the members of the service team. Participants were required to select and paste the appropriate "bubbles" with the preferences of the subject of the picture.

Extreme UX cases

Participants were asked to imagine how Foursquare would function if the company did not develop an app for smartphones.

Iterative transformation of the subject

Four participants in the task draw one object in each of the corners of a piece of paper and pass this piece of paper to the fifth participant. Now the one who got the sheet will have to find one item, to which the rest can be “reduced” in several iterations.

Organizing your cover collection

Each employee received a ZIP archive containing 100 different covers of music albums and singles. The participants were required to categorize all the covers in the way they wanted to.

Telestration

The first employee writes a phrase on a piece of notebook. The second illustrates it on the next sheet. The third writes on the next page what he thinks is shown in the illustration. The next - illustrates the phrase written by the third - and so on, until the notebook returns to the first participant.

Saudade

Saudade is a word that does not have an exact translation into Russian and means nostalgia, longing for the departed. The participants of the meeting were asked to come up with something that would help some person to cope with this longing and for a while “reunite” with those who are no longer with him. The team's suggestions include a tattoo with the coordinates of every place a person has ever called home, or a "super creepy" shawl made from the skins of dead cats.

Website redesign on office sticker

Each employee presented their own version of the redesign of one of the pages of the Foursquare website. The only restriction set for participants was that only one sticker could be used.

New sticker design for Swarm

Assignment: come up with a new sticker for the Swarm app and tell its backstory.

"Pimp My Ride"

Each participant of the meeting was offered to draw the car of his dreams.

Team board game

Employees are divided into several teams, and each team member is given the task of painting part of the board game field. At the same time, members of one team do not see what their partners have drawn.

"Your Morning in 2065"

Each participant had to draw how he sees his morning in 50 years. What will be outside the window, what will he eat for breakfast, what news will he read and how.

beer tap design

To complete this task, the employees had to come up with a new beer brand, and after that - to mold a figurine that would be installed on the beer tap in bars as a handle.

Entertaining puzzles for non-standard thinking

Paul Sloan and Des McHale

Translation from English. N. Chupeeva; illustrations by Myron Miller

INTRODUCTION

The brain needs and benefits exercise. These puzzles are a kind of mental fitness course aimed at developing your ability to think outside the box. You can even do an additional exercise when you hear the answers.

The puzzles contained in this book consist of unusual, often far from real life situations. Each of them has a perfectly logical explanation. You have to get to the bottom of the matter every time. The "Clues" section contains leading questions and hints in case you find yourself in a dead end. Perhaps you will enjoy these puzzles more if you solve them not alone, but with friends, colleagues, etc. It will be best if someone who knows the solutions to the puzzles will answer the questions asked by other group members. Questions should be formulated in such a way that they can be answered with the words “yes”, “no” or “not relevant”.

When you take on puzzles, it's best to test all your assumptions and hunches. Ask questions broadly and clearly to find out what is really going on in the situation at hand. You will have to be both logical and relying on the power of your imagination. When a series of questions leads you nowhere, you will have to approach the solution "from the other side." That's when the ability to think outside the box will play its decisive role.

The puzzles contained in this book are divided into 4 main groups with two tests Vaslyu included in the text for variety and easy respite. The easier tasks are included in the "Testing puzzles" section, and the most difficult ones are included in the "devilish puzzles" section. There is also a section "Terrible puzzles" in this book. They are all about death, accidents or injury. Such puzzles are among the most popular, but scrupulous and fastidious readers have a hostile attitude towards this kind of riddles. And here are the tests Vaslyu, may appeal to the most cheerful readers. These quizzes are specifically designed to make you laugh.

The world needs people who can think outside the box and find new, original approaches to solving current problems in all areas of life. Humanity needs people who can come up with exciting new solutions to the problems we face. Our puzzles are, of course, primarily entertainment. But for all that, they can help form a new legion of people who can think outside the box.

PUZZLE

1. Test puzzles

1.1 A story about a fish

One woman had a very dear favorite to her - gold fish. Once a woman noticed that the fish in the aquarium did not swim as before, weakened and withered. Then this woman took the fish to the veterinarian, and he told her to come back in an hour. When she returned, the woman saw that her goldfish had become as mobile as before, and seemed to have recovered. How did the veterinarian manage to cope with such a task?

1.2 Missing passenger

Little Billy was only 4 years old, and his father and mother were no longer in the world. The man who took care of Billy sent him by train to the village where Billy was now to live. Billy couldn't read or write.

He also did not know the place where he was sent. Only the big sign that hung around his neck could help Billy get where he wanted to go, because that sign had his name and destination written on it. However, despite all the efforts and all the goodwill of the railway employees, Billy never got to the village where he was sent. Why?

One woman approached a man behind the counter and handed him a book. The man looked at the book and said, "You have four dollars." The woman paid the said amount and left without taking the book. The man saw the woman leave empty handed but didn't call her back. Why?

1.4 "Hairy" problem

Why, by and large, does the hair on a man's head turn gray before his moustache?

Two naturalists, determined to protect nature and save endangered species of animals and plants, are talking to each other. One says to the other, "I liked the way you hit that bird." The second replies to this: “Yes, it turned out well, but worse than what you did with a big bird.” What were these naturalists talking about?

1.6 Blinded while drinking tea

One man was drinking tea when he suddenly became blind. What happened to this person?

1.7 Miscalculation

One person slowly counted something, but, unfortunately, lost count. A little later, he felt a sharp pain in his back. Because of which?

1.8 Weather forecast

John was watching TV. Immediately after the midnight news, the weather forecast was announced: “It is now raining, which will not stop for two next days. However, in 72 hours it will be clear and sunny.” "They're lying again," John snorted. He was right, but how did he know the prediction was wrong?

1.9 You won't look at the West...

Agree that at the North Pole it is impossible to look at the North, and at the South Pole - at the South. Where, then, would you be if you could look North and South from there, but could not look either East or West?

1.10 Beggar

The beggar had a brother who died. What is the relation of the beggar to the dead brother? (Answer "Brother" do not give.)

1.11 Truck driver

The police officer saw a truck driver moving in the wrong direction on a one-way street, but made no attempt to stop the driver. Why?

1.12 Mountains ahead

You are sitting next to the pilot of a small plane 1 mile above sea level. Huge mountains are visible right in front of you. The pilot does not change speed, direction, or altitude, but you remain unharmed. Find an explanation for this.

1.13 Strange baptism

During the christening ceremony godmother the baby is suddenly grabbed by the priest who leads this ceremony, pushes him so that he is on the floor, and then she rolls the priest on the floor. Why is she doing this?

1.14 Pond problem

One person wants to get to an island located in the middle of an ornamental pond, and at the same time remain dry. There is a distance of 20 feet from each side of the pond (see drawing), and a person has 2 boards, each of which is 17 feet long. How will this man be able to get to the island?

1.15 Walking and running

Once upon a time there were two avid sportsmen. One evening, exactly at 6 pm sharp, one of them started on foot at a speed of 4 miles per hour, and the other started on a bicycle at a speed of 12 miles per hour. An hour later, each of them stopped. Then both of them ran for 15 minutes at a speed of 8 miles per hour. Both athletes started at the same point A. Both moved all the time in the same direction, never changing course and not resting for 45 minutes. Both reached point B at the same time. How could this happen and what was the distance from A to B?

1.16 Church bells I

One detective lay in bed Sunday morning listening to the bells of the local church. Suddenly he realized that he was listening to a phonogram. How did he guess about it?

1.17 Church Bells II

One night the vicar noticed that the old church clock struck 13 at midnight. The same thing happened the following midnight, and the vicar checked the mechanism of the clock. The mechanism turned out to be in perfect order, but the clock again struck 13 strokes. Why?

1.18 Popular book

When this book was first published, only a few very wealthy people read it. Now almost everyone has a copy of this book, and many people often look into it. However, you cannot buy it in a bookstore, just as you cannot take it in a library. What is this book?

1.19 River crossing problem I

One man came to the river, bringing with him a fox, a duck, and a sack of grain. Near the very bank of the river, he saw a boat in which it was possible to transport only a fox at a time, or only a duck, or one sack of grain across the river. A man could not leave a fox alone with a duck, or a duck "alone" with a sack of grain. How did this man get the fox, the duck, and the sack across the river?