Newest Questions
29,037 questions
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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