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7
votes
5answers
1k views

If done everyday, it's civilized. If only done when something's wrong, it's nasty

When speaking of doing this everyday as a daily routine, this is a civilized thing to do. When speaking of doing this only when something's wrong, this is a nasty thing to do. What is this thing we ...
4
votes
3answers
406 views

Functional inequality?

Find all functions $f:\mathbb{R}\to\mathbb{R}$ s.t. for all $x,y\in\mathbb{R}$, we have $$yf(x)+f(y)\ge f(xy)$$ Problem from the my math olympiad training problem set few weeks before. Functional ...
8
votes
1answer
284 views

A riddle for the highway

I'm laying on the highway, but you can't drive over me, for as soon as you're over me, I'm over you. What am I?
31
votes
5answers
5k views

How can 3 queens control the white squares?

It is well known that there is no way of arranging 4 queens on a checker board in such a way that every square is occupied or threatened. Now consider a slight variation where we only need to cover ...
10
votes
1answer
326 views

A Cryptic Cryptarithm

An entry in Fortnightly Topic Challenge #48: Unusual tag mix Solve these puzzles to reveal why I made them. Matriarch mostly prepared oats for American airline location? (8) AIRLINE + LOCATION = ? 51 ...
5
votes
1answer
283 views

Triangles, rectangles, nonagons

Which is the nonagon with the least area and which fulfills the following conditions. The nonagon has to be made from 7 triangles and 3 rectangles, all having side-lengths that are integer numbers. ...
0
votes
0answers
152 views

The nice and round sequence

I have thought up a sequence, and I name it the nice and round sequence. Its first 10 numbers are 15773, 29694, 165083, 276316, 496325, 498512, 702504, 719466, 808667, 826245 What is its pattern? ...
-4
votes
2answers
107 views

maximum product of n positive integers whose sum is k

We have to find n numbers such that $$ x_1 + x_2 + \cdots + x_n = k $$ $$ x_1 * x_2 * .....* x_n = maximum $$ What are the values of $x_1, x_2...x_n$ ? Note that $x_1, x_2...x_n$ are all positive ...
10
votes
1answer
254 views

A Full Spread of Vowelburgers™

Inspired by Avi's Vowelburger™ Riddle I ordered some Vowelburgers™ abroad, but every menu had a printing error, so the restaurant just got rid of them. Regardless, they had something for everyone, ...
2
votes
1answer
75 views

Number conversion via Prime route

This is a variation of the Word Ladder. Instead this is a number ladder. Convert the number 12345 to the number 54321 in seven or less steps with the following rules A: You can only change any one ...
4
votes
4answers
559 views

maximum product of n numbers whose sum is k

We are given two numbers, n and k. We have to find n numbers such that $$ x_1 + x_2 + \cdots + x_n = k $$ $$ x_1 * x_2 * .....* x_n = maximum $$ What are the values of $ x_1, x_2, ...x_n$ if these ...
9
votes
2answers
601 views

A Triangle of Squares

Let $T(n) = 1 + 2 + 3 + \text{...} + n$ be the $n$th triangular number. For which $n>1$, if any, is it possible to split the first $\frac{n(n+1)}{2}$ positive integers into $n$ sets, all of ...
10
votes
1answer
397 views

Grid infection with diagonal adjacencies

A community consists of 81 houses laid out in a 9 x 9 square grid. Every household is friends with their eight orthogonal and diagonal neighbors (except for the houses on the perimeter which have only ...
4
votes
1answer
272 views

An Anime Affix Riddle

An entry in Fortnightly Topic Challenge #48: Unusual tag mix My prefix hosted* talk to beat a killer from within. My infix works for former bandit, shooting with their twin. My suffix can be found in ...
9
votes
1answer
347 views

What is an Ants Letter™?

This is a variant on the What is a Word/Phrase™ series started by JLee. If a letter conforms to a special rule, I call it an Ants Letter™. Use the following examples below to find the rule. Ants™ ...
18
votes
9answers
3k views

A fun lateral-thinking Chess puzzle [closed]

Which famous movie is suggested by the following chess position (by Trevor Tao)?
13
votes
4answers
610 views

Domino tiling on 8x8 checkerboard with four squares removed

I once posted this problem on the (now deleted) Area 51 Math Puzzles proposal. It was well-received there, but obviously I didn't get an answer. I still don't know the answer, and I'm not even sure if ...
7
votes
2answers
833 views

What is this terrible place?

Cross me, and you'll never return. Play with me, and you'll never see the dawn. Renew me, and I'll give you Hell. Yet don't worry, for as much as you pursue me, You'll never reach me. Who am I?
2
votes
4answers
199 views

The Greenhouse Problem version 2

This is an extension of Nilster's great puzzle: The Greenhouse Problem The task is the same, but this time sprinklers cover only a 3x3 square around them. For completeness, here is the full set of ...
2
votes
1answer
167 views

How long will it take to hand out the shuffled papers?

A teacher has $n$ students sit in a circle in her classroom. She holds in her hands a perfectly shuffled stack of the students' graded homework, with Juan's on top. She is currently standing in front ...
-3
votes
1answer
155 views

What is a TEXT Word™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles. If a word conforms to a certain rule, I call it a TEXT Word™. Use the ...
2
votes
2answers
119 views

Make a difference. First you rise, then you fall

With me you can make a difference. With me reversed, I'll rise and I'll fall.
15
votes
1answer
343 views

Earth Science | Chemistry + Flags

An entry in Fortnightly Topic Challenge #48: Unusual tag mix Which famous chemist is represented by these flags? Go big or go home!
22
votes
2answers
987 views

What is a Prebus Word™?

An entry in Fortnightly Topic Challenge #48: Unusual tag mix (Somewhat in the spirit of the What is a Word™/Phrase™ series started by JLee, a special brand of Phrase™ and Word™ puzzles.) If a word ...
15
votes
4answers
1k views

The Greenhouse Problem

While I was playing a certain popular indie farming game, I came across a dilemma. I have a greenhouse that I'd like to fill as efficiently as possible. How many plants can I fit in the greenhouse? ...
8
votes
1answer
475 views

Meat, metal and Mediterraneans

Across 1. One heavy metal group's farewell (5) 5. Actor who won an Oscar for taking off clothes in Ice Age (4) 7. Way to pay for immigration paperwork? (4) 10. Unfinished show makes permanent ...
-12
votes
3answers
164 views

In computer science Using the digit 4 exactly four times and 4 signs only and only the operation + is allowed how to get 10? [closed]

in computer science Using the digit 4 exactly four times and 4 signs only and only the operation + is allowed how to get 10? for example: $(44 - 4) / 4 = 10$ does not work because 44 is a number ...
4
votes
2answers
279 views

Mathematics for the English major

An entry in Fortnightly Topic Challenge #48: Unusual tag mix I was looking at the unusual tag mixes post, and one of the ones listed is combinatorics and english. I thought "who's going to be ...
8
votes
1answer
396 views

An Anagram Tribond: You can love it, or not

An entry in Fortnightly Topic Challenge #48: Unusual tag mix Figure out what these mixed up clues are supposed to be and solve the tribond, then repeat with the results! Group 1: tubings, pertain, ...
4
votes
3answers
170 views

Experts at failure

Construction challenge: Find a position with the longest sequence of unique losing moves, i.e. white to move has one and only one move that will lead to a lost (for white) position. White makes this ...
6
votes
1answer
161 views

The Five Main Ones

Here is a classic A is to B as C is to D puzzle. Try see if you can figure out the answer. $F:BRW::I:GRW::P:GR::R:BRY::?:?$ Note: Some minor simplification was needed on some of them. But that ...
14
votes
1answer
2k views

Oh No. I had those today

Who? That miserable, Sick man Was poisoned? Eleven letter word
10
votes
1answer
220 views

Cryptic crossword: a little je ne sais quoi

Ten clues have word-play and definition that appear not to match. The result of the word-play must be entered into the grid. To assist solvers one extra letter appears in the word-play of all other ...
-1
votes
4answers
236 views

Travelling around the world [closed]

Μy destination is a part of the world. Part of the destination, when read backwards, is a living thing, and another part of the destination, scrambled, is a delicious meal. What part of the world is ...
13
votes
1answer
401 views

A conspiracy threatens!

I need help! While cleaning the office desk of my boss, I discovered a letter and I think something really bad is going on. The other day I also saw him sending a message on his phone... And today I ...
6
votes
1answer
225 views

A Cryptic Combination

My friend couldn't make it to school today, but wanted me to grab his backpack from his locker for him. He told me he had a combination lock, and sent the following message, saying "There's one ...
6
votes
1answer
314 views

Mission accomplished?

32811132 74131968 592162 289216 If you can say «mission accomplished», then you are a true ...... Hint:
2
votes
0answers
107 views

The Mantra Riddle

A sentence that can never fail A broken foot without its tail Almost there... reverse one sound By turns mundane and quite profound. The mantra is your compass then Your watch to know exactly when It ...
4
votes
2answers
604 views

Forcing one to stay while forcing one to leave?

There is this word that means to force one to stay. that read backwards, means to force one to leave. What is that word?
9
votes
1answer
162 views

Scrabblescrapers

An entry in Fortnightly Topic Challenge #48: Unusual tag mix In this puzzle, you are given a 5x5 grid that you need to populate with a word square, so that the rows and columns form words (as defined ...
-1
votes
1answer
56 views

As Slaughter Crept unto the Sheep

Turn in my lord! Turn in my lord! But water I cannot afford. Some milk is best at your request. Now hide you and get you some rest. But as he sleep, to him she creep, As slaughter crept unto the ...
3
votes
2answers
383 views

3 x 2 sliding puzzle

Would it be possible to solve a sliding puzzle like this (x is the space)?: 1 3 2 4 5 x I haven't been able to solve this and I don't even know if it's ...
3
votes
1answer
58 views

Sounds like you need something to do

What word am I thinking of? Each group will give you part of what you need. Group 1 split, peel, bunch, dump Group 2 Vermont, Virginia, Tennessee, Kentucky, North Carolina Group 3 Merlin, Percival, ...
5
votes
3answers
220 views

Is this Prime Sequence the longest?

So you are interested in Prime Numbers and puzzles thereof. You saw the following on PSE and gave it a try and got it long after the correct answer was posted by @hexomino. My Eight Cousins But then ...
8
votes
1answer
236 views

Wordsmiths & Wyverns

You awaken in a foul crypt with only the following items at your disposal... ROPE, BOOTS, AMULET, MAP, FLAIL, CHAIN, CUP, BELL, STAFF, RING, CODEC, RUM, FLUTE You also have the following tools. Awl (...
14
votes
2answers
588 views

Now you're Packing with Portals #2: Hashtag

Place the colored shapes into the white area, without rotations or reflections, so that they fill it perfectly. The gray walls don't just block shapes, though - they act as portals! When you place a ...
0
votes
2answers
94 views

The Poem of Love and Grace [closed]

Here is a simple poetry riddle I just thought up. Enjoy! A king, so great, lives fifteen years more, A giant, so mighty, his power so easily tore. A shepherd, in the wild, a stick to a snake, A death,...
6
votes
1answer
226 views

Foo Clue and Who?

A simple puzzle I thought of during a work-from-home-session today. Enjoy :)
-2
votes
1answer
91 views

Is asking your one question by doing an action an answer to the two doors, two guards puzzle? [closed]

Is asking your one question while doing an action an answer to the two doors, two guards puzzle? Example: You ask your one question by moving towards any door. Only the true guard will continue to ...
6
votes
1answer
125 views

The Abysmal King

What was the king's name (missing from the riddle), but more interestingly, what was the king trying to hide? Slay me now, and take a solemn vow, Men can't say I might have died this way, Thrust ...

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