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The plague of mice
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The plague of mice

In a certain city, in the face of a brutal plague of mice, cats that each hunted the same number of rodents were used. It is known that 1,111,111 were the hunted mice and less than 1,111 the cats involved. Although there was no physical evidence on the exact number of mice that each cat hunted, this data is recorded in the official records.

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North Pole Research

A research team is in the North Pole conducting a study on climate change. During the transmission of the daily information to the central station there is a problem in the communication so that the measurement scale corresponding to the ambient temperature of the base is not received correctly.
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Ugly, dumb and bad

According to a curious statistic 70% of men are ugly 70% of men are silly and 70% of men are bad. Knowing this, over a hundred men, how many of them will be both ugly, dumb and bad? Solution It can be any number between 10 and 70. We know that, of the 100 men, it may be that 30% are not ugly, another 30% are not stupid and another 30% different from the previous ones are not bad.
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Saving for my birthday

On January 1, I started saving for my birthday party. On the first day I saved a coin, on the second day I saved two coins, on the third day three coins and so on until the day of my birthday when I managed to save 276 coins. What day is my birthday? Solution January 23.
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The coin bag

A group of friends find a bag with 56 coins. They do not know very well how to distribute them since they cannot do it in equal parts so one of them comes up with a solution: Each of us will throw a coin in the air, if it goes expensive, it will take 5 coins and if it leaves a cross, it will take 6 coins Once the distribution was over, there was no money left over and we know that among those who received 6 coins there were two brothers.
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A calendar of cubes

In this calendar, to indicate the day the cubes are placed so that their front faces show the date. Each of the faces of both cubes has a number from 0 to 9 distributed so that we can build any day from 1 to 31 if we orientate them properly. What are the digits that contain each of the cubes?
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The difficult Hexa-trex

The objective of the Hexa-Trex is to find a continuous path that passes once through all the boxes to obtain a valid equation. From the image board, what is the way to go to get a valid equation? Solution The following image shows the solution:
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The swag of the bat

In a period of five consecutive nights, a bat has captured 100 insects. If every night you have captured 6 insects more than the previous one, how many mosquitoes did you capture each night? Solution During the five consecutive nights he captured 8, 14, 20, 26 and 32 mosquitoes respectively. A simple way to calculate it would be to divide the 100 mosquitoes by 5 nights which will give us the central value: 20.
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Playing with perspective

In this case, the images we present show different objects at different distances. The perception of the proximity or remoteness of the objects is made from the lines that converge at a vanishing point. Thus, in the images that we present to you, figures of different sizes are shown and the question we ask is if you are able to find the largest figure in each image.
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Guess the figure

In the image on the right you can see the shape that is achieved from the cutout shown. It is a cube. Would you be able to find which figure is formed with the following cutout? Solution This is an icosahedron: You can find more information about this geometric figure on Wikipedia.
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Pawn Race

On a chess board, we place a pawn in its usual starting position, in the second row. We want to crown the pawn by taking it to the last row following the following rules: The pawn will advance as many squares as faces we get from the launch of a certain number of coins, which we assume balanced.
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The three fastest horses

At the county fair a vendor has 25 horses for sale. He assures us that everyone is very fast and that none runs at the same speed as the others. We want to buy three horses to participate in the races of the racecourse and the seller allows us to run them in races of a maximum of 5 horses each to find the fastest.
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Looking through the window

Look closely at this picture. How are the windows located? Do you think that these are two facades of the same building that we are contemplating from one of the corners? Or maybe it's the building's patio and the man looking out the window is looking at his neighbor's window. The truth is that the artist plays with the perspective so that we cannot affirm whether it is a situation or another.
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The bear ride

A bear in search of food walks 10 kilometers to the south, then walks 10 km to the east and finally 10 km to the north. At that moment he realizes that he is back at the starting point. What color is the bear? Solution The bear is white because the situation described occurs in the North Pole.
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Look for the eagle

Pixel Art is a digital art form with photo editing programs or graphic applications that allow pixel-level work. In this image an eagle hides like the one we show here: Are you able to find it? You can find this and other examples of Pixel Art here. Solution
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It happened in 1864

A famous mathematician wrote in 1864: "At some point in my life, some years ago, the square of my age coincided with that year." In what year was the mathematician born? Solution If we call na the age he was in 1864 and consider that x "years" earlier that "moment" took place, then we have that in the year (1864 - x) he would be (n - x) years old and the given condition will be expressed as the following way: (n - x) 2 = 1864 - x Since we know that n must be a positive and natural integer, the only valid solution is: Therefore, we must find a value close to 1864 whose root is a natural number.
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The rotating gears

The image shows four gears that are connected to each other. Gears A and D each have 60 teeth while gear B has 40 teeth and C only 20. When turning the system, which gear will spin faster, A or D? Solution Both will rotate at exactly the same speed. The gears of equal measure rotate at the same speed regardless of the number and size of the gears between them.
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A, B and C

A, B and C are worth 1, 2 and 3 although we don't know which letter each value corresponds to. To find out, they give us the following clues: If A is not 1 then C is not 3 If B is 1 or 2 then A is 3 If C is not 2 then A cannot be 3 If C is not 1 then A is not 3 Yes C is 3 then B is not 1 or 2 If B is 3 then A is not 2 Solution A = 1, B = 3 and C = 2.
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The three clocks

At home we have three watches. On January 1, all of them marked the correct time, but only one of them worked precisely. Another one was late 1 minute per day and the third one was ahead 1 minute daily. After how long will the three clocks re-mark the exact time? Solution After 720 days, the three will mark the correct time again.
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The broken calculator

My calculator has one of its keys broken so that when pressed it appears a number that is not the one corresponding to the key. If I type all the numbers from 9 to 1: 987654321, a number divisible by 11 appears on the screen and leaves a remainder 3 when divided by 9. What is the broken key?
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The problem of socks

In the bedside drawer I have 28 black socks and 28 white socks. When the alarm rings, it is still dark and in order not to wake my sleeping brother in the same room, I avoid turning on the light. How many socks do I have to take to make sure I have at least one pair of the same color?
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