A detachment of 100 soldiers must pass a very deep river, but the bridge is destroyed. Suddenly the commander sees two children sailing in a small boat near the shore but the boat is so small that it only fits one soldier or two children and no one else. How many boat trips were necessary so that all the soldiers could cross the river with the boat and how did they do it?
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My daughter has as many sisters as brothers and each of her brothers has twice as many sisters as brothers. How many sons and daughters do I have? Solution I have 4 daughters and three sons. Each daughter has 3 sisters and three brothers and each son has 4 sisters and two brothers, twice as many sisters as brothers.
Andrés and Berta want each one to buy the history book. Andrés is missing 7 euros to buy it and Berta 1 euro. If they raise the money they have, they can't even buy a book for both of them. What is the price of the book? Solution The book costs 7 euros. Andres had no money and Berta had 6 euros.
The bank teller could tell us some interesting experiences that occur in the daily routine and some curious problems that arise in the form of puzzles. What would you do, for example, when an elderly gentleman who, like most mortals is reluctant to give us a 200-dollar bill and tells us: “Give me some 1-dollar bills, ten times more 2-dollar bills and rest in 5 dollar bills. ”
There is a town inhabited by sincere people and other liars, where half of the population is crazy and the other half is sane. A sane person believes that all true statements are true and believes that all false statements are false. A madman, on the other hand, believes that all true statements are false and believes that all false statements are true.
Place the numbers from 1 to 8 on the following board so that the number placed in each red box must be equal to the sum of the numbers placed in the white boxes that surround it: Solution 6 7 1 8 4 2 5 3 To reach the solution we can make the following reasoning: It is obvious that the number 8 cannot be placed in the white boxes since any sum with this value would return a number greater than 8.
My brother and I are very fond of the coin game. It consists of placing 20 coins on a table so that alternatively we are taking one, two or three coins, as desired by each player. The player who withdraws the last coins wins. Is there any strategy to always win? Solution The winner is the last one who withdraws coins, that is, the first of the players with one, two or three coins left.
Using all the numbers from 1 to 9 and without repeating any, find three numbers of three figures each such that the second is double the first and the third is triple the first. What number is it? Solution The numbers are 219, 438 and 657. The result is obtained by scoring taking into account that the five can only go in the second position of the third number, since its double is ten and it is not possible to place zeros, nor is it double of no integer nor can it be triple because five would be repeated.
To return home from school I always use the bicycle. There are two possible paths to get to my house: the first one is completely flat and the second one goes up halfway and the other half down. When I go on the way up, I go twice as slow as when I go down on the ground, but on the way down I go twice as fast, so it will take me the same to arrive regardless of the path I take.
Juan wanted to add all the four-figure capicúa numbers but forgot to add one of them. What number did you forget if the sum obtained was 490776? Solution We will try to find a shortcut to add all the capicúas that Juan should have added and then we will subtract the amount he has obtained.
A 400-meter-long train crosses a 600-meter-long tunnel at the same time when another train twice as fast and half-length crosses a triple-length tunnel. Which train will (completely) leave the tunnel first? Solution If we apply the formula: speed = space / time we have that the time it takes for the first train to completely exit the tunnel is: For the second train of half length: 200m, triple tunnel length: 1800 and double of speed: 2v we have to: That is to say that they take exactly the same to leave the tunnel.
Ana emptied a matchbox on the table, distributing them in three different piles. In those piles there were a total of 48 matches and he observed the following: “If from the first pile, as many matches as there were initially in the second and then from the second step to the third, as many matches as there were in this third pile and then, from the third a lot happened to the first as many matches as there was at that time in the first, at the end of this process the three piles will be the same ”.
In the late 1970s, China imposed the one-child policy to try to contain the country's growing population so that each couple could only have one child. What family kinship relationships will cease to exist in China? Solution There will be no brothers, uncles, nephews, cousins or brothers-in-law.
If a child and a half eats a candy and a half every day and a half, how long will it take four and a half children to eat four and a half candies? Solution If every child and a half takes a day and a half to eat a candy and a half, four and a half children will also take a day and a half to eat four and a half candies since the number of children and consumption are both multiplied by 3.
The following dice game is very popular at fairs but it is rare for two people to agree on the chances of winning the player has, so I present it as an elementary problem of probability theory. On the board we have six boxes marked with the numbers 1, 2, 3, 4, 5 and 6.
Hugo was born on a rainy Sunday in Paris in April and turned seven on a sunny Sunday in Tokyo. How old were you in 1996? Extracted from the page lolamr.blogalia.com Solution Birthdays are repeated on the day of the week every six years (there is only one leap in between), but at the end of the century, due to astrophysical correction, despite being leap they do not have One more day in February (look at 2000).
A 3 cm diameter coin can pass through a 2 cm diameter hole, without forcing or tearing it. How? Solution We make a round hole of 2 cm in diameter in the center of a sheet of paper. The sheet of paper is folded on itself 3 or 4 times as shown in the image, using the hole as a vertex, thus obtaining a funnel.