# Category Briefly

"Hope and patience are two infallible remedies, the safest and softest, to rest while adversity lasts." Burton "When you have finished accepting that your dead died, you will stop crying and recover them in the memory so that they continue to accompany you with the joy of everything lived ...".

Only one of the following statements is false. Which? A ray reaches a temperature higher than the surface of the sun. Scientists have discovered that dogs can smell the presence of autism in children. Giraffes can clean their ears with their tongue, which measures half a meter.
Let's see if you are able to find a nine-digit number that meets the following conditions: All digits 1 through 9 must appear only once The number must be divisible by 9 If we delete the last digit on the right, the number must be divisible by 8 If we delete the last two digits of the right, the number must be divisible by 7 If we delete the last three digits of the right, the number must be divisible by 6 If we delete the last four digits of the right, the number must be divisible by 5 If we delete the last five digits of the right, the number must be divisible by 4 If we eliminate the last six digits of the right, the number must be divisible by 3 If we delete the last seven digits of the right, the number must be divisible by 2 If we delete the last eight digits on the right, the number must be divisible by 1 Solution Call the number ABCDEFGHI where each tra will represent a different digit.
Santa Claus was in a very bad mood when he discovered that some of his elves had stuck sandpaper on the skis of his sleigh. Of the 8 suspect elves, only two told the truth in the investigation that was carried out, which allowed the joker elf to be discovered: Silly: It was Puk who did it.
In this image, at a glance we see stairs that climb from left to right. This is because it is the most "natural" way to see them. However, the image does not have enough information about perspective and it is also possible to see the inverted staircase so that the “wall” that we initially saw closer may be the farthest and the stairs are turned upside down.
Approximately 3% of births correspond to twin brothers. Knowing this, will the percentage of twin children in the population be greater than, equal to or less than 3%? Solution The proportion will be greater than 3%. If out of every 100 births 97 correspond to single child births and 3 correspond to twin births, we will have 103 children of which 6 will be twins which represents approximately 5.8% of the total.
A metal container full of honey weighs 6 kg, and full of water weighs 3.5 kg. If we know that honey weighs twice as much as water, how much does the container weigh? Solution If honey weighs twice as much, changing water to honey means putting twice as much water. That is, as it goes from 3.5 to 6 kilograms, we are actually increasing 2.5 kilograms.
The date of the last Monday of last month, added to that of the first Thursday of the following month, gives a result of 38. If we know that both dates belong to the same year, would you know what month we are in? August solution. To add 38 it is only possible that it is the highest date for the last Monday of the month, that is 31, and the highest for a Thursday of the month, that is 7.
Can you see the skull in the foreground? And the romantic scene? Look closely, because in the center of the image there is a couple in love declaring themselves. This double image effect is often used by painters and cartoonists. The further we move away from the image, the better the silhouette of the skull can be seen since our vision prevents us from seeing the details with precision.
The other day they showed me a curious watch chain designed according to the old custom of carrying a string of coins attached to a watch. This particular chain consisted of four coins and the effigy of an eagle. The coins, as seen in the illustration, respectively had five, four, three and two holes so that the links that linked them could be placed in different ways generating a wide variety of designs.
Here is another railway puzzle that illustrates a beautiful mathematical principle and at the same time shows us a moral. "I am pleased to see that many cows have more common sense than some men." Casey thought philosophically. Casey was on the railroad bridge the other day quietly contemplating the water when suddenly he saw the light of the express that was just twice the length of the bridge beyond the other end and was approaching ninety miles per hour.
Lucy was born on a sunny Sunday in Hong Kong and turned seven on a gray and rainy Sunday in Macau. How old were you in 1996? Solution Lucy turned 100 in 1996. Birthdays can only fall on the same day of the week every seven years if there is not a leap year between them. 1900 was not a leap year because it is not divisible by 400, so Lucy had to be born in 1896, because the next leap year was 1904.
When everyone left for the great annual picnic, each vehicle carried exactly the same number of people. In the middle of the road, ten of the vehicles broke down, so that each of the remaining ones had to take one more person. On the way home fifteen more vehicles broke down, so that during the return trip there were three more people in each vehicle than when leaving in the morning.
To go from Villarriba to Villabajo I use a car that, when traveling down a mountain, runs at 72 km / h, on flat land at 63 km / h and uphill at 56 km / h. If it takes 4 hours to go from Villarriba to Villabajo, to return to work 4 hours and 40 minutes and we know that there is a flat part of the route, how far is Villarriba from Villabajo?
In this optical illusion you will see the figure of an animal. You will probably see that it is a duck with its beak to the left. Are you able to see the rabbit too? Solution The duck's beak becomes the ears of a rabbit that is looking to the right. It is easier to see if we tilt the image slightly to the right until we get a more natural position of the rabbit's head.
A farmer and his wife go to the market to exchange their poultry for cattle knowing that eighty-five chickens equals one horse and one cow. It is also known that five horses have the same value as twelve cows. "John," said the wife, "let's take as many horses as we have already bought, so we will only have seventeen horses and cows to feed during the winter."
By sorting all the digits from 1 to 9 in some way, are you able to construct a 9-digit prime number? Solution It is impossible since any number formed by the nine digits from 1 to 9 is a multiple of 9, since the sum of those nine digits is 45, a multiple of 3 and 9 and therefore divisible between 3 and 9.
The bakery in my neighborhood sells rolls at 30 cents per unit. It also sells them in packages of 7 rolls at € 1 or in packages of a dozen for € 1.80. My mom gave me a € 10 bill and told me to buy 60 rolls and keep the change. I want to buy at least 60 rolls and keep as much money as possible.
In a magic square, the arrangement of numbers is such that the sum of all rows, columns and diagonals is always the same number. On this occasion, the problem is to create an “antimagic” square using all digits from 1 to 9 so that the sum of all rows, columns and diagonals are different numbers.
Without the help of the calculator and in a reasonable time, take all 4-digit numbers, that is, from 1000 to 9999 and add them. What's the score? Solution One possible way to do this could be the following: We calculate the sum of the numbers from 1 to 9,999 and then subtract the sum of the numbers from 1 to 999 since they should not have been taken into account.
Alberto won the award of a bar in the building of the association of shy anonymous members only. Since the space was reduced, he mounted a bar along the entire premises and 25 stools arranged in line in front of the bar. Due to the type of people who come to the bar, the bar is usually half empty since every time a member of the association enters they feel as far away as possible from any other member and never sit next to each other.