Can you solve it? The deductive decade – ten years of Monday puzzles | Mathematics
Forgive me for the indulgence of celebrating ten years of this column. Toot toot!
I started to publish bihebdodaries breakers at the end of May 2015, originally addressed to you as “Guzzlers” – Guardian Puzzlers. The creaky currency did not stand, but the column did, and here we are a decade and 260 columns later.
Some data. The total of the pages views is now 38 million, which is on average about 150,000 views per puzzle – a huge number, I would say. Thank you all for encouragement and support.
For today’s offers, I decided to come back by the archives and republish ten of my favorites. Some may be familiar, others not.
Please graze, maybe even Guzzle – and here are the next ten years!
1. Bat and ball
Three friends (A, B and C) play ping-pong. They play in the usual way: the winner remains on and the loser awaits their turn again. At the end of the day, they summarize the number of games to which each played:
Played 10
B played 15
It played 17.
Who lost the second match?
2. Delicate trams
Why are the tram air cables positioned to make a zigzag, rather than the straight line?
3. Read the question
3. What is Never strange or even?
4. Catch the cat
A straight corridor has 7 doors one side. Behind one of the doors is a cat. Your mission is to find the cat by opening the right door. Every day you can only open one door. If the cat is there, you win. If the cat is not there, the door closes and you have to wait the next day before you can open a door again.
If the cat should always sit behind the same door, you could find it at most seven days, opening each door in turn. But this mischievous Moggy is restless. Every night, he moves a door to the left or one right at random. Although if it is behind the first or the last door, it has only one option to know where it can move.
How many days do you need now Make sure you can Catch the cat?
5. Mystery number
I have a ten -digit number, ABCDEFGHIJ. Each of the figures is different, and
-
A is divisible by 1
-
AB is divisible by 2
-
ABC is divisible by 3
-
ABCD is divisible by 4
-
ABCDE is divisible by 5
-
ABCDEF is divisible by 6
-
ABCDEFG is divisible by 7
-
ABCDEFGH is divisible by 8
-
ABCDEFGHI is divisible by 9
-
ABCDEFGHIJ is divisible by 10
What is my number?
[To clarify: a, b, c, d, e, f, g, h, i, and j are all single digits. Each digit from 0 to 9 is represented by exactly one letter. The number abcdefghij is a ten-digit number whose first digit is a, second digit is b, and so on. It does not mean that you multiply a x b x c x…]
6. Cub of disappearance
This image was not tampered with. Explain why the reflection has a yellow lion.
7. Crazy triangle
Show that there is a triangle, whose sum of the three heights is less than 1 mm, which has an area higher than the surface of the earth (510 meters2).
8. Pont dilemma
Your friend randomly chooses a card from a standard game of 52 cards and maintains this hidden card. You must guess which of the 52 cards is.
Before your supposition, you can ask your friend one of the following three questions:
-
Is the card red?
-
Is the card a facial card? (Jack, Queen or King)
-
Is the card the ace of bsaps?
Your friend will respond honestly. What question would you ask who gives you the best chances of guessing the right card?
9. The question without question
(a) All the following elements.
(b) None of the following.
(c) Some of the following elements.
(d) all of the above.
(e) none of these elements above.
[Just to reassure you, nothing has been omitted here.]
10. Plus triangle
Find a way to fold a piece of square paper in an equilateral triangle. The triangle can be of any size.
I will be back at 5 p.m. from the United Kingdom with the solutions.
Please, no spoilers instead, please recommend your favorites from the 260 that you have read here over the years.
Sources: 1. Adrian Paenza, 2. Kvantik Magaizine, 3. Des Machale, 4. New York Times. 5. John Conway, 6. Matt Pritchard, 7. Trần Phương, 8. Henk Tijms, 9. Parabola, 10. The Paper Puzzle Book.
I have been putting a puzzle here on alternative Mondays since 2015. I am still looking for big puzzles. If you want to suggest one, send me an email.
