Questions tagged [no-computers]
A puzzle designed to be solved without using calculators, online decoders, or computer programming. Using a computer to type and post the answer is allowed; the spirit of this tag is to make people solve the puzzle on their own.
797
questions
-8
votes
1
answer
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Puzzling rectangles [closed]
Can you find two unequal rectangles whose areas add to $5\sqrt5$?
No computer solutions please.
- 2,917
9
votes
3
answers
870
views
Heteropalindromes in a Word Square
Say hello to a not-so-simple, 4x4 word square:
This little monstrosity has two rules; to define the first rule, have you ever heard of a heteropalindrome?
Strings of letters that form words when ...
- 10.6k
0
votes
1
answer
165
views
How do I ring my friend's doorbell?
My friend, a curmudgeon who dislikes visitors, recently installed a puzzle-doorbell. It consists of ten push buttons in a row, labelled from left to right:
...
- 711
19
votes
3
answers
3k
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The Thieves and the Gold Bars
Two thieves (Rod and Lia) carry out a big heist and steal 16 gold bars. They get away in their car when they run into a bad accident and the car is completely wrecked. Luckily they survive with their ...
- 39.2k
3
votes
2
answers
793
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Most points on a circle
What is the most number of integer lattice points that lie on the circumference of a single circle whose radius is 80 or less? Please no computer computations.
- 33.1k
8
votes
1
answer
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Life, uh, Finds a Way
[Rated PG-13 for language}
I saw someone wearing a "Life happens" t-shirt, which is a fine enough sentiment, but not the most common turn of phrase. It made me wonder...
How fast can you ...
- 3,730
31
votes
2
answers
3k
views
Sum of the first 86 square roots
Without using a calculator or a computer, can you compute the sum of square roots of the first 86 natural numbers, rounded to the nearest integer? In other words, we are looking for $\sqrt{1} + \sqrt{...
- 33.1k
22
votes
3
answers
1k
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Knight tour on a racetrack
Help the chess knight complete four clockwise laps on this racetrack, so that he lands on every square and never lands on the same square twice! The final square the knight lands on will be the same ...
- 32.1k
3
votes
2
answers
279
views
Seven 2s with seven math operations
Linked to A four digit number using exact same 4 digits
A number with same repeated digits is called a Repdigit or Monodigit number
https://en.wikipedia.org/wiki/Repdigit
Can you write an equation for ...
- 39.2k
4
votes
1
answer
398
views
Hero Worms and The Minotaur
And so, Wormeus had a great time, eating every apple in sight, surviving several close calls with the Pink Lady Stickotaurs, respawning after the occasional horribly squishy death, exploring different ...
- 7,434
8
votes
1
answer
196
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Going off on multiple tangents
Given two disjoint circles of diameters D1 and D2 draw all shared tangents. Find the intersection points of all pairs of tangents. Discard those collinear with the two circle centre points. Of the ...
- 19.1k
7
votes
2
answers
549
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Triangles to diamonds
Given a triangle ABC with sides a=|BC|,b=|CA|,c=|AB| a diamond is circumscribed around the triangle's incircle. The diamond and the triangle share the corner C along with (part of) sides a and b.
...
- 3,886
1
vote
1
answer
131
views
Can you pick up an extra shift?
I was going through some old documents the other day and found some instructions for a one way cipher:
Given a word w, iterate over its characters. For each character c, determine if its zero based ...
- 10.6k
12
votes
6
answers
4k
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A four digit number using exact same 4 digits
ABCD is a 4 digit number where A,B,C and D are 4 distinctly separate digits between 1 and 9.
Using any of the following math operations and the digits A,B,C and D exactly once get the number ABCD.
...
- 39.2k
5
votes
1
answer
138
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Wormeus and the Multiple Stickotaurs (Part 2)
This is the sixth puzzle in the Wormeus series and the second puzzle involving multiple Stickotaurs and wormhole puns. Wormhole-pairs are indicated with light green lines (note that this was ...
- 7,434
8
votes
2
answers
635
views
When was Ensquare born?
Professor Matlogic posed this question to his smartest math student:
"Famous mathematician Ensquare was born on this day, this month and this year AD at this time (hour and minutes) pm. True to ...
- 39.2k
6
votes
1
answer
1k
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Three cups and a ball
I am walking down the streets of Paris when a street performer approaches me. He has a row of 3 cups facing down on a table. He places a ball under the left cup. He proceeds to swap pairs of cups, ...
- 33.1k
5
votes
1
answer
187
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Wormeus And The Multiple Stickotaurs
Here is the fifth maze in the Wormeus series. This time Wormeus is faced with multiple Stickotaurs and multiple Universes. Different universes are connected via … wait for it … drum roll ...
- 7,434
8
votes
3
answers
2k
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Changing WATER to STEAM
How do you change the word Water to the word Steam by changing one letter at a time? The newly formed words must be from Merriam Webster dictionary. No proper nouns, abbreviations or acronyms. No ...
- 39.2k
7
votes
1
answer
333
views
AnaCross II: it's bigger now
So, I've prepared another AnaCross puzzle. The rules are exactly the same: At the end of each row is a pool of letters; those letters are the letters that go in that row of the crossword. Normal ...
- 3,909
4
votes
2
answers
201
views
Cyclic squaring
Find a complex number $a$, which satisfies the following conditions:
If you square $a$, you get a different complex number $b$.
If you square $b$, you get a complex number $c$, which is different ...
- 5,686
8
votes
4
answers
1k
views
A Five City Loop, starting and ending in MA
Complete a loop of five large cities.
The starting city name starts with the letters MA. Each of the following cities starts with the last two letters of the previous city name. (Like PARIS ISTANBUL ...
- 39.2k
7
votes
1
answer
803
views
Inequality derived from a famous problem
Let's have the following inequality: $\frac{2}{3}(\sqrt 5-1)^3\lessgtr\sqrt[3]{2}$.
Which part is greater, the left or the right? No calculator solutions are accepted.
- 2,917
6
votes
1
answer
604
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Flat share share
This is a sequel to Gentrification in Chessshire.
Due to the febrile state of the Chesster housing market you and your flat mates are forced to rent out half your place to another group of sharers.
...
- 19.1k
3
votes
1
answer
280
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Quadruped Mosaic
This is a visual puzzle (known as "mosaic" or "fill-a-pix") with the same rules as MineSweeper:
This puzzle has exactly 100 x 100 cells.
The grid is to be filled with colored and ...
- 766
16
votes
1
answer
1k
views
What number goes in the ?? box?
A simple pattern puzzle
What is the number in the ?? box? Why? No programming please.
- 39.2k
-1
votes
1
answer
93
views
Consecutive number division puzzle 2 [closed]
Find 4 consecutive numbers that divide 𝑤, 𝑥, 𝑦, 𝑧 respectively, where 𝑤, 𝑥, 𝑦, and 𝑧 are also 4 consecutive positive numbers greater than 1, or prove it's impossible.
Bonus: What if w > the ...
- 137
5
votes
2
answers
266
views
Wraps and Loops—Some Concrete Examples
This puzzle serves as the more concrete sequel to my previous post; in particular, see that post for the rules of the game. Rather than (implicitly) demanding a description of a polynomial-time ...
- 2,339
2
votes
2
answers
390
views
Four Mathematicians, Four Poker Hands and Four Clues
These four mathematician friends play poker every Saturday night. They always have a twist for the very last hand, just for fun.
This Saturday the twist was “Factorial Clues”. The rule for the last ...
- 39.2k
8
votes
5
answers
690
views
What a coincidence or eighteen is not seventeen take two
Since I botched my first attempt at posing this puzzle, let me try again, this time hopefully closing all loopholes by dropping the packing angle and making this a purely geometric puzzle:
The figure ...
- 19.1k
7
votes
2
answers
2k
views
Eighteen is not seventeen
This question is not the same as Adding coins inside a ring of coins
From a pile of equal size perfectly round coins take eighteen and make a perfect ring. Show that you can fit at least sixteen more ...
- 19.1k
12
votes
1
answer
223
views
Wormeus and the Stickotaur (maze 3)
This is the third maze in the Wormeus series. Previous puzzles are here and here
This shouldn’t be too difficult but contains a cute gimmick that isn’t possible in the original Theseus mazes sans the ...
- 7,434
3
votes
1
answer
101
views
Divisors ending with digits 0-9 each
What is the smallest positive integer, which has - for each of the digit 0-9 - a divisor ending with this digit?
- 11.9k
7
votes
1
answer
304
views
A 3x3 grid with common factors
A $3 \times 3$ grid $G$ is filled with every number from the set $\{2,3,5,6,7,11,14,15,30\}$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that ...
- 33.1k
10
votes
4
answers
991
views
Deriving a 3x3 grid from another one
A $3 \times 3$ grid $G$ is filled with every number from $1$ to $9$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that are greater than $G_{ij}$....
- 33.1k
1
vote
1
answer
118
views
Self-indulgent numbers
Let's call a positive integer N self-indulgent of degree K>2 if for every positive integer k<K the following is true:
More than half of the first k multiples N,2N,...,kN of N contain with ...
- 19.1k
8
votes
1
answer
455
views
Manual tiling with 8 dodecadudes
Here are 8 dodecadudes. (Drawn from the very numerous dodecadrafters, made from 12 half equilateral triangles, dodecadudes are a subset of 770 pieces with sharp points and narrow necks excluded). ...
- 3,788
8
votes
5
answers
1k
views
Split 1 through 6 into a product of 24 and sum of 12
How many ways are there to split the numbers 1, 2, 3, 4, 5, and 6 into two groups, such that the product of the numbers in one group is 24 and the sum of the numbers in the other group is 12? An ...
9
votes
1
answer
203
views
Wormeus and the Stickotaur (maze 2)
Here is another Wormeus maze, following a previous puzzle that is yet to go viral. Wormeus has to eat all the apples without dying a horrible squishy death at the hands of the Pink Lady Stickotaur.
I ...
- 7,434
12
votes
3
answers
1k
views
Swapping 3 knights in a 4x4 grid
Can you swap black and white knights in this 4x4 grid? There is one important constraint: at no point can a knight be under attack by an opponent knight. Knights move using standard chess moves (L ...
- 33.1k
20
votes
1
answer
691
views
Quartum non datur
Can you give a good rational approximation of
$$\sqrt[3]2 \times \sqrt[4]2$$
without doing any significant maths?
Hint:
Attribution: Mine.
- 3,886
12
votes
2
answers
492
views
Wormeus and the Pink Lady Stickotaur
Wormeus lives in a labyrinth containing lots of apples. His main ambition in life is to eat as many apples as possible but his nemesis, the evil Pink Lady Stickotaur, has other ideas – if you pardon ...
- 7,434
12
votes
1
answer
694
views
AnaCross: A crossword made of anagrams
This is a new type of puzzle I've devised: the AnaCross. Nothing new under the sun and all, I'm sure someone has made one before, but I've never seen it.
The rules are pretty simple. At the end of ...
- 3,909
2
votes
0
answers
215
views
This ᴀɴᴅ That musical act from the past [closed]
Below is a fill-in-the-blanks three-part list
of variously-venerable musical acts of the form
“________ ᴀɴᴅ ʜɪs/ᴏᴜʀ/ᴛʜᴇ _________.”
The example of
“Paul Revere ᴀɴᴅ ᴛʜᴇ Raiders”
has been filled in for ...
- 21.8k
2
votes
1
answer
1k
views
Probability of a successful DT Cannon
In multiplayer Tetris, there are a number of opening setups that let you send powerful attacks very quickly. One popular opening is the DT Cannon, which allows the player to very quickly send a T-Spin ...
- 2,434
3
votes
1
answer
166
views
Non-increasing arrangement
We are arranging the numbers from 1 to 8 in an order so that three consecutive terms cannot be increasing. For example, 12345678 isn’t allowed but 81436572 is. How many ways are there to do it? Please ...
- 1,943
21
votes
1
answer
758
views
Escape from Sudoku!
An entry in Fortnightly Topic Challenge #50: Escape Rooms
I hesitated to enter this in the Escape Room FTC, but I definitely was inspired by the challenge to create this puzzle, and it is, in some ...
- 26.3k
4
votes
1
answer
1k
views
Find three ways of forming the number 100 using 3,3,5,7
As it says in the title.
Rules:
anything not explicitly allowed is forbidden.
use 3, 3, 5, 7 and multiplication, division, sum, difference, unary minus, and exponentiation in any order. Parentheses ...
- 3,886
12
votes
1
answer
508
views
Three white queens, two white knights, and one rook on a chess board
On an 8 x 8 chessboard, place three white queens, two white knights, and one white rook so that every cell of the board is under attack by at least one piece not standing on it.
Source: https://www....
- 16.9k
4
votes
1
answer
201
views
Chess - I will eat!
Suppose that you are playing White, and your aim is to eat a black piece (pawns qualitfy) in the fewest moves as possible and Black are not cooperating at all, and, even more, Black's aim is to ...
- 5,963