Most active questions
114 questions from the last 30 days
20
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7
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Dissect the figure into two congruent parts.
Dissect the figure into two congruent parts.
Clarifications:
Shape ABCD is a square.
Points A, B and E are collinear.
Circular arc AE has center C and radius marked with the arrow.
Attribution:
May/...
- 27.6k
24
votes
4
answers
2k
views
Dividing a hexagon into 9 equal regions
Can you divide a regular hexagon into 9 regions of equal shape and area?
- 38.7k
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
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
15
votes
5
answers
905
views
Stein Coins for Local Terra - Place 8 Double-Sided Mirrors!
Stein Coins for Local Terra
Place 8 double-sided mirrors to make the lasers from the alphabet go to its corresponding place, which is the same alphabet.
(The mirrors should be placed diagonally, / or ...
- 2,712
15
votes
2
answers
2k
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Can you construct a 3x3x3 cube using 9 red, 9 green and 9 blue unit cubes such that there is no “line” of 3 unit cubes that are all the same color?
You have 9 red unit cubes, 9 green unit cubes and 9 blue unit cubes. Using these 27 unit cubes, you construct a 3x3x3 cube.
In such a 3x3x3 cube there are a number of “lines” of 3 unit cubes where ...
- 27.6k
19
votes
3
answers
1k
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Can you get all the coins no matter where they are placed?
I have placed a dime in nine of the 36 squares of a 6x6 grid. All coins are visible.
You may choose three rows and three columns and take all the coins you find in them. You can look at the grid and ...
- 27.6k
29
votes
2
answers
1k
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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
5
votes
7
answers
2k
views
The Twin Brothers and the Judge
Based on a Raymond Smullyan question from "Lady or Tiger".
A judge must reveal which one of them committed a certain murder. He knows that one of them always lies. He is only allowed to ask ...
- 2,192
6
votes
3
answers
1k
views
Magic fifteen. Who wins the race to 15?
Take nine slips of paper and number them from 1 to 9, then lay them face up on a table.
Two players take turns taking one of the numbers (that is, one of the slips of paper).
The game ends when either ...
- 27.6k
12
votes
5
answers
971
views
Fill the circles so that the sum of the three numbers along each of the ten lines is the same.
Using all the numbers 1, 2, 3, ..., 11 (each exactly once), put a number in each circle so that the sum of the three numbers along each of the ten lines is the same.
Attribution: Puzzle by M. Varga ...
- 27.6k
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
17
votes
3
answers
901
views
Can you find sets of 4 (or 5) positive integers such that their pairwise sums give consecutive numbers?
Warmup question:
Is it possible to find four positive integers such that their pairwise sums give six consecutive numbers?
Main question:
Is it possible to find five positive integers such that their ...
- 27.6k
28
votes
1
answer
1k
views
The CXV sequence
This infinite sequence uses simple English and mathematics. Find the next term.
2, 2, 6, 4, 4, 2, 6, 6, 4, 2, 9, 8
- 74k
10
votes
2
answers
823
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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