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.
798
questions
14
votes
15
answers
8k
views
The computer can't do anything I couldn't do with pen and paper
If you want to know how much $3^{100}$ is, you can just type it into a computer and it will spit out a really big number. But that is no fun. The task is to estimate $3^{100}$ with some computation ...
- 1,691
10
votes
2
answers
1k
views
A square number that is a concatenation of at least 25 squares
A pen and paper challenge:
Write down a number whose square (repetition allowed) is the concatenation of at least 25 nonzero squares.
examples
7, 13, 12: Their squares are the concatenation of 2 ...
- 8,010
1
vote
1
answer
192
views
Determine the hidden digits in this long division puzzle
The following problem was given in the Eureka journal (October 1963/University of Cambridge). This problem can be solved by hand without computers. There is a unique solution. Have fun solving!
Fill ...
- 5,878
25
votes
2
answers
2k
views
What is my favorite brand of pen?
This is an entry to the Monthly Topic Challenge #3: Pencil and Paper Games
Given the following valid "tic-tac-toe" boards:
What is my favorite brand of pen?
Other possible tags to check ...
- 24.5k
5
votes
2
answers
374
views
a six-by-six KenKen
The rules of KenKen are as follows:
You must fill in the numbers 1 through 6, one number per box, in the grid, so each row and each column contains each number exactly once.
Each heavily outlined ...
- 12.6k
4
votes
2
answers
438
views
Dark time in prison
You wake up. It is pitch dark. You don't know where you are. You feel groggy.
The last thing you remember is being in a bar, a sexy young woman appeared out of nowhere, walked straight at you, ...
- 26.8k
7
votes
2
answers
1k
views
What are the hidden digits in this long division puzzle?
The following problem was given in the Eureka journal (April 1978/University of Cambridge). This problem can be solved by hand without computers. There is a unique solution. The phrase, "exact ...
- 5,878
3
votes
1
answer
227
views
Sequence of numbers - what comes next? [duplicate]
What is the next number in this sequence, and why?
4 2 3 4 6 2 4 8 3 _?
Also, since people here find sequence questions to be arbitrary, the following uses the same rule. What number is next?
4 5 6 4 ...
- 296
3
votes
1
answer
209
views
Tetromino tilings of a 4x5 rectangle with minimal diversity
This is a relatively easy manual tiling puzzle. In fact the tiling is all done for you, you just have to specify how many of each of the 26 given tilings to use. The puzzle is:
Using N complete sets ...
- 3,798
7
votes
1
answer
505
views
Find all integers n such that $\sqrt{n-4 \sqrt{n-19}}$ is also an integer
The following puzzle is from the December 2012 issue of the Eureka journal (published by The Cambridge University Mathematical Society).
Find all integers n such that $\sqrt{n-4 \sqrt{n-19}}$ is also ...
- 5,878
13
votes
1
answer
2k
views
The Lufthansa Lottery
In order to pass free time while striking for better pay, some Lufthansa workers organise a lottery where
each ticket picks three distinct numbers from $1$ to $11$ inclusive
the draw picks five ...
- 6,996
17
votes
7
answers
1k
views
Efficient Mowing at PSE
Your task:
Find the most efficient mowing path around the dark green bushes that mows (passes over) all of the grass (light green).
For those who cannot view the image above, there are 9 rows of 16, ...
- 17.5k
13
votes
4
answers
809
views
How do I create a sliding-blocks puzzle (specifically like the "Rush Hour" ones) which requires an "ah-hah!" moment?
Background
My grandma gave me a set of Rush Hour puzzles as a small child, ever since I could be trusted to not eat the pieces. I still enjoy playing these today and would like to try my hand at ...
- 10.1k
4
votes
1
answer
147
views
Find the 3 Item Amounts
Last week the store's receipt printer removed lines randomly from each item amount.
A technician repaired the printer, but now it adds lines randomly to each item amount!
The cashier told me that for ...
- 17.5k
18
votes
3
answers
754
views
Find the Two Item Amounts
I bought 2 items yesterday and the receipt was incorrect, so I asked the cashier about it.
She told me that
The receipt printer had been acting funny recently.
The total is always correct, but some ...
- 17.5k
6
votes
1
answer
298
views
Riley-Clued Crossword
The no-computers tag is there only to prevent database dictionary searches. Other computer uses are fine.
Below is an ascii version of the image above, for those who cannot view images. All words are ...
- 17.5k
0
votes
1
answer
263
views
Sum of digits of numbers
Let S be a function such that S(N) is the sum of digits of N. N belongs to natural numbers, and N < 10²³. N does not contain a zero digit in it. The numbers are in base 10.
Find the number of N ...
- 1,334
9
votes
3
answers
1k
views
Elegant solution to this digit puzzle
Puzzle
The letters $a, b, c, d, e$ and $f$ represent single digits and each letter represents a different digit. They satisfy the following equations:
$$
a+b=d, \quad b+c=e \quad \text { and } \quad d+...
- 7,010
17
votes
3
answers
2k
views
No Computer Allowed (Beware the Eater)
The answer is a relevant single word. No computer or digital calculator allowed. Beware the eater of red herring, if you happen to spot it.
6 - 5 + 4 + 7 = ?
7 + 8 + 8 - (7-5) - (7-1) = ?
6 - 5 + 7 + ...
- 24.5k
21
votes
1
answer
596
views
A wordsearch for today
Sixteen 4-letter words have been concealed in the grid below, as well as one word that is much larger.
Can you find all seventeen words?
Text version of the wordsearch (for copy-paste purposes):
<...
- 133k
12
votes
1
answer
554
views
A massive synonym
Please explain how to assemble the puzzle.
Yes, one is missing, but you can follow the >.
No computers.
Hint:
Hint 2:
Hint 3:
Text version:
...
- 24.5k
10
votes
2
answers
614
views
An overconfident grandmaster
Suppose you are playing a grandmaster with the White pieces and you are on the verge of losing the game.
The overconfident grandmaster offers you a bet: You will make two consecutive moves with White ...
- 1,334
4
votes
2
answers
226
views
Using Prime numbers to get 100 and 1000
Using the digits 1 to 9 exactly once create a set of one or two digit prime numbers.
Use those prime numbers and the math operations + - / * and
parantheses to get 100.
Then use those exact same ...
- 39.2k
7
votes
2
answers
462
views
It is all in the past
Presented here are questions related to past tense words I researched and googled that resulted in this designed and developed puzzle. Got it?
Which past tense word (PTW) is also a past tense word ...
- 39.2k
12
votes
3
answers
1k
views
Adding consonants to create an antonym
This is an emotional word with 2 vowels
Starting with it create two words by adding 2 different consonants.
The two new words are antonyms of each other. See below. What is that word? No programming ...
- 39.2k
6
votes
2
answers
579
views
Five words, Five vowels, Five last names
These five words are from the Collins English Dictionary.
Are also last names,
And have one vowel difference in exact same location and same
consonants in exact same locations.
Example : Last Lest ...
- 39.2k
5
votes
2
answers
631
views
A Complicated Exercise In Addition
Another day, another walk down to the cafe. I was waiting in line for my coffee, wondering what the barista could do this time to make my name look whack. But as I waddled in line, a curious site ...
- 8,253
7
votes
1
answer
1k
views
Can you stop the falling piano with 23 nets?
MIT's Baker House has a tradition of dropping an irrepairable piano six floors every Drop Day, the last day one can drop a class without penalty (the 2022 date is 19 April). This year, in order to ...
- 6,996
7
votes
1
answer
963
views
Binary Sudoku Puzzle
The rules of Binary Sudoku are quite simple. It is very similar to regular Sudoku, except here we try to fill a 9x9 board with only black and white tiles following the below rules:
Every row, column, ...
- 81
10
votes
2
answers
559
views
Permutations of first 10 natural numbers such that all the prefix sums are distinct
I posted this question on Math SE as well. Did not receive any help.
This is a question that I was asked in a Quant Interview. I would like you all to have a crack at this. I could not find a problem ...
- 201
5
votes
2
answers
241
views
How many coins did Raj get?
I found a bunch of coins: Quarters (25 cents), Dimes(10 cents) and Nickels(5 cents). The combined amount was a whole two digit number of dollars: that is, no fractional amount.
I divided the coins ...
- 39.2k
4
votes
1
answer
660
views
5
votes
1
answer
201
views
Fill in the blanks with numbers
A simpler version of this puzzle was by @Sid on PSE
Fill in the blanks with the number in words
Here is a bit challenging version
Fill in the blanks with numbers (in words) for the following:
This ...
- 39.2k
2
votes
1
answer
557
views
Thirteen Diagonals of a Nonagon
A regular nonagon has 27 diagonals, and these diagonals intersect in the interior of the nonagon at 126 distinct points.
Show that it is possible to select 13 diagonals of a regular nonagon such that ...
- 13.4k
30
votes
1
answer
844
views
PSE Advent Calendar 2021 (Day 20): Candy Cane Sudoku
This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2021. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door >
So I was ...
- 26.5k
3
votes
1
answer
430
views
Genies' chess on a 10×10 board
The work of Hearth Taxel revealed some other results related to genies' chess. For example, there is an arrangement $A$ of pawns on a 10×10 board such that no 3×3 submatrix is empty and
$A$ is ...
- 6,996
14
votes
2
answers
840
views
PSE Advent Calendar 2021 (Day 4): Decorating with Ingrid Deduction
This puzzle is part of the Puzzling StackExchange Advent Calendar 2021. The accepted answer to this question will be awarded a bounty worth 50 reputation. < Previous Door Next Door >
"...
- 26.5k
32
votes
2
answers
3k
views
Three missing digits in 42 factorial
When calculating $42!=42\cdot41\cdot...\cdot2\cdot1$ the result is
$42! = 140500611775287989854x14260624y511569936384z00000000$
However three digits have been replaced by $x$, $y$, and $z$.
Can you ...
- 11.9k
4
votes
1
answer
156
views
Copy that solution
This copy machine program prints
the solution to a well-known puzzle.
Explanation of the syntax will follow.
What solution will be printed for which
well-known puzzle?
EXECUTION CODE
.--> ...
- 21.8k
7
votes
3
answers
570
views
A Grand Game (Find two words)
Find 2 relevant (but not strictly related) words using a logical method. One ends in 'R', the other in 'E'.
The method should be one which leads to the exact and specific letters for each word (no ...
- 24.5k
3
votes
1
answer
208
views
Some blissfully ignorant math?
I was playing around with the code for my game the other day in an effort to create some unique effects. One thing I created was what I called an "ignorant assignment" in which I applied ...
- 10.6k
4
votes
1
answer
241
views
Fractions and Fractional Numbers
Using fractions and fractional numbers of the digits $1$ to $10$ and only the mathematical operations of addition, subtraction, multiplication, and division, including parenthesis (e.g. $1 + 2 - (3 * ...
- 39.2k
3
votes
2
answers
322
views
Consecutive integers which have digital sums that are not relatively prime
What are ten smallest natural numbers n, such that n and n+1 have digital sums which are not relatively prime?
- 16.9k
2
votes
1
answer
238
views
What number comes next in this evenly doubled sequence?
I've been playing around with sequences lately and found a pretty evenly doubled sequence of single digit numbers:
1, 12, 30, 64, 65, 156, 175, 368, 369, 371, 752, 753, 1524, 1525, 3060, 3073, 6168, ...
- 10.6k
1
vote
1
answer
173
views
An oddly formed sequence?
I've been playing around with sequences lately and came across one that was rather, odd.
$101$, $123$, $147$, $189$, $191$, $213$, $217$, $279$, $...$
Hints
Let $N_i = 101$...
Can you determine the ...
- 10.6k
3
votes
1
answer
483
views
A number like waldo?
What is the smallest whole number that when its individual digits are summed, produces a number 4 digits long? For example, the number $5357$ is no where close since $5 + 3 + 5 + 7 = 20$.
Note: I'm ...
- 10.6k
9
votes
4
answers
2k
views
This Unusual Year
Our current year, 2021, has the unusual property that the digital sum (the sum of the digits) of its square is precisely equal to its digital sum squared. Indeed: 2021^2 = 4,084,441, whose digital sum ...
- 16.9k
2
votes
2
answers
209
views
Powerful Octagon
Place different integers on the vertices of an octagon so that the sum of the integers in any two vertices joined by one of its edges is a power of 2. Do so in such a way that the largest integer used ...
- 16.9k
5
votes
3
answers
352
views
The Thieves and the Gold Bars II: Greed and Distrust
Two thieves, Bo and Jo, steal 7 gold bars and are driving away when their car is wrecked in an accident. They-and the loot- is intact.
They are at Point A at 8 PM and must go to Point B which is 1 ...
- 39.2k
11
votes
1
answer
240
views
Tiling three pears with three-pair hexominos
The 21 hexominos below are all those that can be made by joining three dominos together (i.e. they have a perfect matching with respect to the graph of their squares) and are not rectangles. The ...
- 6,996