All Questions

Filter by
Sorted by
Tagged with
0
votes
1answer
7 views

Multiples of their reversals

8712 and 9801 are the only 4-digit numbers which are multiples of their reversals: 8712 = 4*2178 and 9801 = 9*1089. Without using a calculator/computer, can you find two 5-digit numbers with this ...
0
votes
0answers
4 views

Numbers that are the sum of the cubes of their digits

There are just four 3-digit numbers which are the sums of the cubes of their digits. For example: 370 = 3^3 + 7^3 + 0^3 and 371 = 3^3 + 7^3 + 1^3. Without using a calculator/computer, can you ...
9
votes
1answer
169 views

Mathematical golfing

You have probably heard of code golfing? There the task is to find the shortest computer program that produces the required output. Here we want to perform math golfing - find the shortest formula ...
3
votes
2answers
66 views

Find the missing shape

Here's a grid of shapes: Which of the following shapes should go in the missing cell, and why? There is only one correct answer, and the explanation should not be very complicated.
15
votes
5answers
1k views

Creating the hardest 10x10 maze

You are given an empty 10x10 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A robot is programmed to start in the top-left corner of ...
5
votes
5answers
172 views

Move two matches (no [lateral-thinking])

Move two matches to make the following equation correct: Despite it commonly applying to puzzles of this kind, there is no [lateral-thinking] tag here, so no spelling out numbers, no turning the ...
0
votes
2answers
83 views

Assessment Centre Logic test

I have to exercises with solutions (red) from a german assesment centre logic test which I not understand: Does anybody the logic behind them?
3
votes
3answers
130 views

Complete this cross sequence

What is the next element of this sequence and why? Possible choices: Hint
1
vote
2answers
52 views

Can someone solve this sudoku without trial and error? Please explain

Stuck in this sudoku. If anyone can solve this then please share the method.
4
votes
1answer
171 views
+300

Scrambler puzzle (CTF forensics problem by me!)

Before anyone starts hyperventilating, this is not part of an ongoing CTF! I just made this example CTF problem for fun... To learn more about what a CTF is, check out this Wikipedia page. For this ...
2
votes
1answer
84 views

Find the equation of this surface - The Snowman

Here is a surface that resembles a snowman: Its equation has the form $f(x,y,z)=0$: if a point $(x,y,z)$ satisfies that equations it is shaded, otherwise it is "left blank". Your goal is to find $f$. ...
1
vote
0answers
41 views

Find the next number in the given sequence

I created this puzzle. Find the next number in the sequence and the logic behind it. $$2, 1536, 5, 1792, 23, 1184, 53, 1168, 113, 1048, 137, 1384, 179, 1576, 311, 1268, 431, 1234, 719, 2026, 1031, ...
5
votes
1answer
65 views

How can this puzzle be solved without guessing?

This puzzle was given to my 8 year old from the school. My child was struggling, so I gave it a bash, but was unable. I do sudoku regularly so know most methods of solving. I gave it to my husband and ...
11
votes
2answers
98 views

Look at me - a number sequence

This sequence goes on forever, but here is the first 7 of them. The X's are just there to hide the actual digits. Can you find all the correct digits of the 8th entry? 1024, 90X1X, 25023X, 490364, ...
11
votes
5answers
631 views

A mouse and a maze on a n x n grid

I went back in an old Flash game and was intrigued by this problem. Rules There is an $n\times n$ grid and a mouse entering on the entrance cell and exiting on the exit cell. The entrance ...
14
votes
1answer
613 views

No trap in this one

This visual puzzle resolves to a number. HINT Hint2 Hint3 Hint4 Hint5 Hint6
2
votes
1answer
58 views

How to understand this line in the solution to this puzzle?

I'm trying to understand the solution to a puzzle named "Expelled," the link to which is here. Most of the solution to the puzzle makes sense to me, except the most important part -- how to determine ...
8
votes
1answer
70 views

Cryptic Family Reunion: Unclaimed Ignition (Fan-Made)

Inspired by the Cryptic Family Reunion Series by Jeremy Dover. The answer to this puzzle is a list of seven thematically related words or proper names or phrases. Each of these is clued cryptically,...
3
votes
1answer
92 views

Phone pattern security

My phone is unlocked using a security pattern. This is a path drawn through a 3x3 grid of dots with the following rules: The path can start at any dot The path visits neighbouring dots: horizontally,...
6
votes
1answer
250 views

One code to rule them all

Kurt, our crusty old mainframe admin, finally retired last week and I've been given the task of sorting through his files. Most of the files were comprehensible, if not understandable, like his old ~/....
9
votes
2answers
302 views

Cryptic Exile by Sir Featherwait

Just the other day I met Sir Featherwait in the professional aviators' lounge, where he instructed me to guess his favorite anime. Unfortunately, it seems that every guess I made went further and ...
9
votes
2answers
337 views

It's everywhere (yes, everywhere)

Here are 16 words which can be divided into 4 groups of 4 each. PLASMAS HUM EPIC BENZ OBSC MUND COND HIST GRAVEST CONS EXT CAROT ARC OVERT ...
6
votes
2answers
768 views

Wait, it is worth it?

You went to a Casino, and saw a quite interesting stall. The cardboard besides the stall says: You first pay \$$5$ You have to toss the fair coin. If it lands heads, you can ...
0
votes
0answers
32 views

How do I solve this Vigenere puzzle? [closed]

I have tried vigenere cipher's decoders but they don't work. This is what it is: Wutg iyr rhw xosw qeonf, "yhrtrid no stmot shsindy gsyr." Can someone please help me?
0
votes
2answers
97 views

Triangular pool and three swimmers [closed]

Given a triangular pool 100, 120, 140 yards and three swimmers which swims at rates of 3.5, 4.0, 4.5 yards per second - place them on the edges of the pool in such way that when they start swimming at ...
9
votes
0answers
86 views

Alice and Bob invent a game

The rain was still falling in Wales, and Alice and Bob were terribly bored of having to stay inside the caravan. With just a deck of cards to entertain them they had played all of the card games in ...
3
votes
1answer
79 views

It's all in the 2's follow-up question

This is in regards to the solution in Slitherlink - It's all in the 2s I know it may seem dumb, but I don't understand the logic behind the second 2 chain in the solution. To help provide clarity ...
6
votes
1answer
81 views

Cryptic Family Reunion: Accentuate the Positive

The answer to this puzzle is a list of ten thematically related words or proper names or phrases. Each of these is clued cryptically, and the theme is to be determined. Since the definition part of a ...
4
votes
2answers
258 views

Creating the hardest 7x7 maze

This puzzle is based on Creating the hardest 6x6 maze You are given an empty 7x7 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A ...
2
votes
0answers
144 views

The cryptic treasure hunt

I created this puzzle. This may be really challenging. But I assure you that there is a solid logic behind. (Note: Questions are cryptic) 1: Ucbemfol.jcancyf 2: Mwamebyr;assdpwhbporcrof; File 3: ...
9
votes
1answer
327 views

A functional equation again!

Determine all functions $f:\mathbb{R}\rightarrow\mathbb{R}$ such that $$(x-2)f(y)+f\big(y+2f(x)\big)=f\big(x+yf(x)\big)$$ for all $x,y\in\mathbb{R}$. Source: Math Excalibur Volume 22, Number 1 ...
2
votes
2answers
84 views

stucked really bad with sudoku puzzle

Stuck with this for long time now, I have tried all the techniques yhat I know
10
votes
4answers
429 views

Floor functional equation

Find all functions $f:\mathbb{R}\to\mathbb{R}$ satisfying the following functional equation: $$f(\lfloor x\rfloor y)=f(x)\lfloor f(y)\rfloor\quad\quad\text{for all }x,y\in\mathbb{R},$$ where $\lfloor\...
9
votes
2answers
140 views

Cut It Up! (then find a phrase)

This is a "sorry for messing up yesterday's clues" puzzle. For each shape below, divide along grid-lines into identical pieces (rotation and reflection allowed). The first shape has 3 pieces, and the ...
15
votes
9answers
61k views

Cutting a cake into 8 pieces

Say, you are given a cake which you must share with 7 others. So, you must cut the cake into 8 pieces. But, you are only allowed to make 3 straight cuts. You cannot move pieces of the cake after the ...
3
votes
2answers
90 views

Tangential circles

The following figure has two axes of symmetry which define its width and length. The length (horizontal distance) is twice the width (vertical distance). The largest circle has a radius of 2005 and ...
37
votes
8answers
6k views

9-5=5? Matchstick problem

Move one matchstick to make an equality. Question made by me (Is this too easy?)
22
votes
1answer
824 views

Hey, This is a 100th Puzzle of Mine!

Yep, this is my 100th puzzle here in PSE~ I'm really having a wonderful time here, thank you so much guys! >< I planned to write a harder and bigger one, but it turned out I was too lazy to do that....
12
votes
1answer
479 views

Slitherlink - It's all in the 2s

Can you solve this Slitherlink puzzle that I came up with? And in CSV: 3 - 3 - 2 - - 2 - 2 - 2 - - 1 1 2 2 1 - - 2 - 2 2 - - - 2 - 1 2 - - 1 - I tried to ...
5
votes
1answer
169 views

What's the puzzle?

Someone sent me a photo of the last few lines of a puzzle. They were: BULLDOZER OVENPROOF BROADTAIL BREAKER ASYNTACTIC TIFF ALKYNE ABOUND EVASIVE BEVERAGE HILARITY COOTIE What ...
9
votes
2answers
264 views

Probability of picking the red marble twice

Start with a bag containing one red marble and one white marble. Reach into the bag and pull out a marble at random. Put it back and do it again. If, on both times, you grabbed the red marble, stop. ...
5
votes
3answers
330 views

Playing the Square Chess

On an ordinary chess board (8x8) without any pieces on it as a starting position, two players will alternately place a pawn on any square (unoccupied) so that the first player that form a square (...
26
votes
4answers
4k views

Creating the hardest 6x6 maze

You are given an empty 6x6 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A robot is programmed to start in the top-left corner of the ...
25
votes
5answers
1k views

Google cannot find me

Google cannot find me, reflected I'm lemon and lime, googling 'me' is when you fall, me and meme will answer all. What am I? Line 1 hint: Posted I still Line 2 hint: Take my reflection ...
5
votes
2answers
510 views

Boggling googling

I'm a number for you to evaluate, Googling 'me' gives the drop off the Empire State, Though the great Google finds no results for me, I'm just a pure integer value you'll see. What number am ...
0
votes
2answers
143 views

Cheapest strategy on average to find specific items in a set

The problem You have a set on N (around 15-30) seemingly-identical objects, which in fact comprises a small number D (unknown, between 1-3) of defective objects and the rest (N-D) are good. There ...
11
votes
5answers
12k views

What is the English word with the greatest number of consecutive repeated letters?

Example: one repeated letter - bitter two consecutive repeated letters - bassoon three consecutive repeated letters - bookkeeper I've tried to find a four-times-repeated example but failed. (...
13
votes
3answers
921 views

Random walking on a board

There’s a pawn starting in the center of this game board. At each move, it can advance randomly towards any of the adjacent squares sharing a common side with equal chance. What’s the probability of ...
11
votes
4answers
1k views

How to make the number 49?

You've to start with $1$ and can use each of the following operations at most once. You can do the following in any order you like: 1) Add $2$. 2) Add $3$. 3) Add $5$. 4) Multiply $2.$ 5) ...
12
votes
2answers
383 views

Fun with Flags part 9: a different design

We are looking for a 3-word phenomenon. Hint 1: Hint 2: Hint 3: Hint 4: Other (independently solvable) puzzles of this type: 1, 2, 3, 4, 5, 6, 7, 8, 10.

15 30 50 per page
1
2 3 4 5
406