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votes
2answers
36 views

Untangle me. Who am I?

I am a kind of tangle. But I don't look like noodles. I may look like a packet of noodle. I do not look like an entangled headphone. But I look more like a smartphone. What am I?
8
votes
1answer
134 views

Functional equation by me!

Find all functions $f:\mathbb{R}\rightarrow\mathbb{R}$ such that $$f(x)f(x+y)=xf(x)+f\big(f(x)\big)f(y)$$ for all $x,y\in\mathbb R$. Source: Problem by me.
3
votes
1answer
153 views

Less than 3 moves?

Sherlock is back in the city to solve mysterious cases. Currently, he is solving a murder case. The dead body is being sent to the forensic lab and now Mr. Sherlock is looking for some clues in the ...
2
votes
1answer
67 views

Kings on a chessboard

Let $n$ be a positive integer. You are given $4n^2$ kings and a $4n\times4n$ chessboard. You have to place the kings on the chessboard such that each row and column contains exactly $n$ kings, and no ...
7
votes
1answer
209 views

Sort 9 trains on 3 paths

On the three paths of a station are A, B, and C types as shown in the figure. A locomotive driver (L) can attach from 1 to 9 trains to a locomotive at any time, move them to the right path, and then ...
7
votes
3answers
336 views

In honour to 2004

222444 is the smallest number that is divisible by 2004 and only contains the digits 2 and 4. What’s the next number that has the same properties? Hint:The number is 11 digits long.
3
votes
0answers
50 views

Good family relationship

Mr.K's message: It's a beautiful day outside! Geese are flying. Remember that my favorite seafood is squid? It's best served with Java waterdropwort! Let's eat them next time we meet,...
7
votes
0answers
81 views

The Odd Street Clocks

The clockmaker took a walk after a lunch from a restaurant and across the block corner he found the old clock box with four similar looking clocks on every wall. It is in the middle of the street ...
7
votes
1answer
105 views

Numbered Countries

I've assigned numbers to several European nations as shown below. My question is: what's my methodology in choosing these numbers? What would the numbers for Estonia, Latvia, and Lithuania be? (Note: ...
4
votes
0answers
45 views

Rubik's M Slice Using Thumb

I've been cubing for a couple of years now, so I'm quite familiar with all the various finger tricks and different ways to move faces and slices. Most of the ones I came up with when I started were ...
-8
votes
0answers
67 views

Diophantine equation with advanced techniques [closed]

How can you solve the Diophantine equation $$x^2-xy+y^2=2019$$ without testing a lot of numbers? I want to see how number theory is used to solve this problem. I rearranged a little to derivate ...
4
votes
2answers
70 views

Find the hidden logic (Easy)

I created this puzzle. What is so special about this number sequence? What is the logic behind this sequence? $$63072, 123172, 123173, 123174, 123175, 123176, 123177, 123178, 123179, 63081, 63082, ...
6
votes
1answer
95 views

My first attempt at a Vowelburger™ puzzle

You can find the other Vowelburger™ Riddles here I ordered 9 Vowelburgers™ with buns and meat at the linguistic restaurant - help me identify each one from the description on the menu! $$ \def\S#1#...
2
votes
1answer
47 views

Another phonetic Vowelburger™ Riddle

You can find the other Vowelburger™ Riddles here I ordered 7 Vowelburgers™ with buns and meat only at the linguistic restaurant - help me identifing each one from the description on the menu! $$ \...
2
votes
3answers
276 views

“phone” into “cord”? (word ladder)

Here's a classic word-ladder for y'all. Can you transform "phone" into "cord", using only single-letter alterations? Rules Each step can either add a letter, remove a letter, or change a letter. ...
3
votes
2answers
117 views

What kind of Room am I?

I am a kind of Room But people cannot stay inside me. People can put some of us inside them. For the rest of us, we don't recommend to put me in you. I am not a washroom, yet I have lot of ...
4
votes
2answers
88 views

Cryptic Friends and Family: The Shining

This puzzle is a cryptic family reunion, but we've invited some close friends that are not actually family. The answer to this puzzle is a theme and a list of fourteen words or proper names or phrases;...
5
votes
1answer
99 views

A dubious sequence

I created this puzzle. Observe the following sequence carefully. $$\text{men, xomt, asem, nub, chesbet, teht, hat}$$ Now answer this question : Why did I run around crazy after this? What's my ...
4
votes
1answer
52 views

See me once, see me twice #13

Long time no see! Here is a fresh one for my "See me once" series: See me once, a pending action is ripe Say me twice, must I now help you wipe? See me once, used in an auxiliary way See ...
15
votes
1answer
460 views

Friday's the most cryptic day of the week

Across 1. War paint for alien entering from space station's entrance (9) 6. An island country's capital, Praia, devastated after the loss of republic's leader (4) 10. Search "engine oil" at first… Got ...
5
votes
4answers
610 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 ...
3
votes
1answer
60 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 ...
1
vote
2answers
76 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.
9
votes
3answers
507 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.
5
votes
2answers
143 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, ...
7
votes
1answer
683 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 ...
1
vote
2answers
113 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
1answer
110 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 $f$. ...
2
votes
1answer
71 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 ...
9
votes
1answer
86 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,...
0
votes
0answers
45 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?
9
votes
2answers
381 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 ...
23
votes
2answers
223 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 ...
0
votes
2answers
104 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 ...
6
votes
2answers
168 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,...
7
votes
2answers
801 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 ...
11
votes
2answers
118 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, ...
9
votes
2answers
338 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 ...
3
votes
2answers
93 views

stucked really bad with sudoku puzzle

Stuck with this for long time now, I have tried all the techniques yhat I know
3
votes
1answer
87 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
85 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 ...
3
votes
2answers
91 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 ...
9
votes
2answers
268 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. ...
25
votes
1answer
928 views
+100

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....
10
votes
4answers
438 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
1answer
330 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 ...
9
votes
1answer
200 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 ...
5
votes
1answer
171 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
147 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 ...
6
votes
2answers
230 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 ...

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