Newest Questions
29,037 questions
0
votes
0
answers
13
views
Beating Harvard scientists
Long ago, Ivan Panin found 30 ways in which `7' is encoded in Genesis 1:1. He challenged Harvard scientists to create an English sentence with just as many multiples of 7. With all their wisdom and ...
- 101
5
votes
1
answer
117
views
Square dissection into 4 congruent polygons with same perimeter length of square itself
How can you dissect a square into four non-self-intersecting congruent polygons such that each polygon has the same perimeter length as the given square?
The goal is to have minimal number of edges ...
- 1,364
8
votes
1
answer
306
views
Maze Run Puzzle 2.0
So, we gave it another go after reviewing and editing the original post. For context, here's the post: Maze Run Puzzle
SUMMARY:
In the last post I mentioned that me and a friend created the maze run ...
- 197
6
votes
2
answers
152
views
Is it possible to put a cooperative checkmate here in three moves?
The puzzle is presented in two versions: full (1) and abbreviated (2).
Is it possible to put a cooperative checkmate here in three moves? (white makes the first move)
h#2,5 (AP) Stepan Nichto. ...
- 304
25
votes
1
answer
706
views
A pair of Find-the-stars puzzles
Find-the-stars instructions:
A Find-the-stars puzzle is played on a square grid that is initially empty except some squares contain arrows.
The goal of the puzzle is to fill some empty squares with ...
- 27.6k
11
votes
2
answers
765
views
Filling a 6x6 square with tetronimoes
Consider a square grid of 6 by 6 cells. Can you fill it with 9 tetronimoes (Tetris pieces)? Sure you can! In fact, there are many, many solutions to that. Here is one:
If there are n unique solutions ...
- 1,567
4
votes
1
answer
345
views
2014 MIT Aquarium Hunt Puzzle #8
Here is the content of the puzzle (or see https://puzzles.mit.edu/aquarium/2014/8.pdf):
Title: MAKE A WISH FOUNDATION
Flavor: Dear Travel Log, This island is inhabited by solemn beings who look like ...
- 141
8
votes
1
answer
683
views
Shortest closed path for pilgrims on planet Cube
The planet Cube is an ordinary cube with 6 faces, pilgrims must visit 6 towns, one on each face. The length of any edge of Cube is 3 miles, the cities have the following coordinates (x,y,z) in miles:
...
- 1,364
0
votes
3
answers
515
views
Maze Run Puzzle
So, a friend and I created this maze puzzle. Have a go.
The rules are as follows:
Doors open in the direction that they point
Once you move through a door, you cannot go back through it
Empty spaces ...
- 197
-5
votes
0
answers
142
views
Estimating a sum of consecutive prime numbers [closed]
$p_n = 0.069n^2 + 2.229n - 1.85 \ $ can be used to estimate the nth prime number for $ \ 1 \le n \le 25.$
Using some combination of arithmetic, algebra, calculus, by hand, and a calculator, please
...
- 2,482
-8
votes
0
answers
99
views
Find the Missing Number in This Intriguing Pattern [closed]
Examine the sequence below:
1, 3, 6, 10, 15, 21, ?
Identify the number that should replace the question mark.
- 1
3
votes
0
answers
152
views
Murder mystery puzzle told through seven news articles [closed]
Project52hz is a puzzle series with different types of challenges, all leading up to something bigger. It’s been tough so far, and only one person on Reddit seems to have made real progress.
The first ...
- 31
1
vote
1
answer
216
views
Can you determine the tasty item?
2111121221
It’s a nice way to end a meal! (7)
This puzzle has nothing to do with phone numbers.
- 27.6k
11
votes
1
answer
928
views
longest path in 10x10 grid
This puzzle is based on a grid that contains values from 0 to 9 and wildcard *.
Find longest non-intersecting path in a matrix starting from top-left cell and ending bottom-right cell.
Build the path ...
- 1,364
8
votes
0
answers
509
views
Two popular bright rivals
Grid missing rival!
Can you figure out who's secretly behind this rivalry? Fill in the nickname accordingly in the grid.
Hint 1:
Hint 2:
EDIT:
Instead of what I've written in the hints above
- 47.8k
11
votes
2
answers
595
views
Make him shuffle most!
James is a dealer who can only use overhand shuffle. For some reason, you decide to harass on him. You know that he is playing a “stacked deck” with some player. You are also good at it, so you decide ...
- 2,712
8
votes
4
answers
367
views
Both, One, Neither… But With A Twist
There are 99 people in a building. All the people are either Agents or Jokers. You know that at least 50 are Agents (they might all be Agents).
You can point to any two people, and ask to any third ...
- 1,974
1
vote
1
answer
119
views
-4
votes
3
answers
210
views
1 22 333 4444 55555 666666 7777777 88888888 999999999
You are given the following 8 numbers:
22
333
4444
55555
666666
7777777
88888888
999999999
Answer the three following sub-puzzles, allowed operators are: $+,-,\div,\times$ and parenthesis.
Obtain 1 ...
- 6,726
3
votes
1
answer
237
views
Breakfast, socks, and diseases
This is my very own logical deduction puzzle I've created with the help of my friend.
It might look difficult, however it is very simple to solve once you make sense of the clues. The multiple ...
- 197
12
votes
2
answers
1k
views
Dissect the almost 10x10 square into 4 congruent pieces.
Your task, should you accept it, is to dissect the following shape into 4 congruent pieces.
Rotations and reflections are allowed. You must cut along the grey lines.
You don't need mathematics to ...
- 32.7k
5
votes
1
answer
689
views
Fastest checkmate by castling
Given that the two chess players cooperate, what is the fastest checkmate with the castle (either White's or Black's) as a final move?
- 6,726
3
votes
1
answer
112
views
Raven's matrix: circles with loops inside or outside
Link: https://sep.stanford.edu/sep/jon/raven/
This is the last question on a Raven's Matrices style IQ puzzle. Question 60 of 60. What is the answer to this puzzle? My guess would be option 2... ...
- 197
6
votes
2
answers
426
views
Making sense of a logic puzzle in Blue Prince parlor room
Context: The game Blue Prince regularly gives the player a specific type of logic puzzle. The setup is that there is a blue box, white box, and a black box. Each box has one or more statements written ...
- 33.3k
17
votes
8
answers
1k
views
Both, One, Neither
There are 99 people in a building. All the people are either Agents or Jokers. You know that at least 50 are Agents (they might all be Agents).
You can point to any two people, and ask to any third ...
- 1,974
10
votes
2
answers
823
views
Can you dissect a 5x9 rectangle into nine (or ten) rectangles and/or squares?
Warmup Question:
Can you dissect a 5x9 rectangle into nine rectangles and/or squares such that all rectangles and/or squares have integer side lengths and none of them have the same dimensions? For ...
- 27.6k
2
votes
2
answers
147
views
A riddle for your time (8)
I mark your thoughts but leave no trace,
I’m silent, swift, and keep your pace.
I vanish fast when you forget,
Yet shape the future’s alphabet.
What am I?
- 986
3
votes
4
answers
199
views
A riddle for your time (7)
Born in a box, I’m killed by light,
I only live when day turns night.
I dance on walls without a sound,
But when it’s bright, I’m not around.
What am I?
- 986
0
votes
0
answers
271
views
pilgrimage speed reference [closed]
Three pilgrims $\alpha$ $\beta$ $\gamma$ plan their journey to pilgrim site $D$ which happens to be equidistant from the sides of a right-angled ($90^\circ$ in $C$) triangle having $a < b < c$. ...
- 2,192
3
votes
1
answer
382
views
How many chess pieces does it take to "cover" all spaces on a chessboard if you must have at least one of each type?
Given an 8x8 chessboard, your goal is to "cover" each space on the board with the fewest possible number of pieces. The extra restriction is that you must have at least one of each type of ...
- 8,494
29
votes
2
answers
1k
views
A puzzling site... But what am I looking for?
After discovering the name of the treasure map’s owner, I came across something entirely different: a puzzling site.
It felt strangely familiar, as if I had seen it countless times before. This time, ...
- 12.7k
8
votes
3
answers
637
views
Can you swap the positions of the 8 Chess bishops?
Goal:
Swap the bishops so that at the end the white bishops completely fill the top row and the black bishops completely fill the bottom row.
Details:
Move bishops one at a time according to standard ...
- 27.6k
10
votes
1
answer
484
views
+50
Satisfying class choice preferences
There are 30 people in a class and each person chooses 5 other people in the class that they want to be in a new class with. The new classes will each be of size 10. Is it ever impossible for ...
- 8,494
2
votes
0
answers
69
views
How to solve this Burr puzzle variation with tile rotation? [duplicate]
Does someone know the solution to this Burr puzzle (interlocking wooden cross)?
This is not a common Burr puzzle, but one where you have to rotate the last piece in place. As you can see in the second ...
- 201
3
votes
1
answer
223
views
What is a Good Word™?
This is inspired by 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 special rule, I call it a Good Word™.
Use the ...
- 2,133
14
votes
1
answer
575
views
"Incomplete rectangles"
I recently called a long-time puzzling friend of mine just to ask if he wanted to join me to this new place in town for puzzle enthusiast. To my surprise he told me that he already was on a trip (...
- 47.8k
9
votes
1
answer
385
views
Reindeer cryptic crossword
Solve on Penpa+
Across
1. Going around to survey cooler waters, ultimately to find some seafood (7)
5. Station C is located next to thrift store (3,4)
9. Disney heroine from popular children's book ...
- 83.7k
21
votes
2
answers
1k
views
Tetris Perfect Clear puzzles
The aim of each puzzle is to completely clear each field, using the listed pieces in order from top to bottom.
"But wait, ApexPolenta," you say, "isn't this just a tiling puzzle?"
...
- 4,347
13
votes
2
answers
361
views
The Flow of Time
Something is haunting me.
Aaaeellmnn Otuvyz
aeh Llnor
dghiin Nsstu
aaeeg Lmrtvv
beei Lnot
eeh Innor
What am I haunted by?
- 20.6k
-7
votes
1
answer
166
views
I’m faint in confusion, Strong in understanding. What am I? [closed]
I’m faint in confusion, Strong in understanding. What am I?
Please post your answer and explain your reasoning.
If you’d like a hint, let me know in the comments.
8
votes
1
answer
703
views
Awake and asleep
Here's a little riddle.
When I'm awake I'm countable, but when I'm
asleep I just go on and on.
What Am I?
- 47.8k
28
votes
2
answers
2k
views
Smallest possible pentomino farm
A pentomino farm is an arrangement of the 12 pentominoes (each of area 5) that satisfies all of the following conditions:
All 12 pentominoes must be used exactly once
Pentomioes must be grid-aligned
...
- 3,456
16
votes
1
answer
2k
views
There are no employees at the store. Why not?
Janice goes to the print shop, but is very confused. There are no employees, but there is a big poster hung on the wall that could explain this. Unfortunately, it's unintelligible.
The sign reads:
<...
- 1,735
-3
votes
1
answer
468
views
A musical ratio
Beginner level puzzle, I guess, or, at least, an easy one.
High reputation members, perhaps refrain to answer immediately
Using only pencil and paper, so without access to any physical CD (Compact ...
- 2,192
20
votes
1
answer
1k
views
19
votes
1
answer
1k
views
Riddle in Cheshire Crossing comic
Looking for an answer to this riddle. I don't know it.
This is from the comic Cheshire Crossing. It is written by Andy Weir who also wrote The Martian.
It is possible this riddle has a real solution, ...
- 745
2
votes
1
answer
271
views
Word Search - Find the hidden words
There are 2 hidden words here, except the given words below:
Words
ACETIC
ACTOR
CRUDE
ERODE
ERUPT
KNOWLEDGE
PEANUT
PITCHY
QUEEN
RACIAL
URBAN
And here’s the code for second hidden word:
...
- 2,712
2
votes
0
answers
203
views
Jane Street INTRO Puzzle
On Jane Street's puzzle intro page:
WHY PUZZLES
What’s a company like Jane Street doing with a page about puzzles? The act of solving puzzles, though that might seem abstract, is intrinsic to the ...
- 3,072
5
votes
1
answer
217
views
Magic World Making
I was born in north center, between a magician and a mathematician.
I keep moving diagonal, north and east, increasing once.
When I meet a north ceiling, I fall to the south bottom, moving east.
When ...
- 2,712
8
votes
1
answer
232
views
Ducks and Penguins
Solve on Penpa+
Across
1. By God, the man's a bastard! (4)
3. Biden has stolen diamonds from POTUS preceding him? That's not allowed! (9)
8. It populates currently unoccupied population centre (4)
12. ...
- 83.7k