# All Questions

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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?
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.
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 ...
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 ...
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 ...
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.
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,...
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 ...
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: ...
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 ...
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 ...
70 views

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### 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 ...
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?
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 $f$. ...
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 ...
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,...
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?
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 ...
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 ...
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 ...
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,...
801 views

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### 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 ...
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 ...
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 ...