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.

Filter by
Sorted by
Tagged with
35
votes
3answers
6k views

First digit of 3^2020

Inspired by The last digit for 3^(2019) Can you find the first digit of 32020 without a computer?
5
votes
1answer
416 views

A unique word: Says Grandpa

"Very interesting word", said Grandpa. "Could be the only word with this property" "What property?", I asked "At least 9 letters long and first four letters are same as the last four letters! ...
6
votes
7answers
1k views

I would like to buy 11 liters of milk please

This is somehow follow up question to How to measure 5 litres using 10L, 7L and 3L vessels You went to a farm to get some milk. You only need $11$ liters of milk and ask for it to the farmer, but our ...
4
votes
2answers
172 views

Another milk jug question

Recently there was a jug pouring competition, and I got to thinking if this was the question with the most number of moves. It turned out that it was. If you have three different sized jugs all less ...
6
votes
1answer
176 views

Numbers with vowels used twice

This question is linked to Numbers in series If you write out the numbers the British way (using "and") What is the smallest number that has all the vowels used exactly twice. What is the ...
4
votes
1answer
199 views

Humans, vampires and mirrors part 2: the triangular mirrors

Find part 1 (without triangular mirrors) here. Here is a room composed of $10 \times 10$ squared cells. Each cell can be empty (𝑋) or contain one of the following: a double-faced mirror ( / or \ ); ...
7
votes
1answer
199 views

What is the minimum-value piece combination necessary to checkmate in this game of Crazyhouse?

Imagine you're playing a game of crazyhouse, which operates like standard chess, except that you have a pocket of captured pieces that you can drop on the board in any legal location as your move. ...
8
votes
1answer
488 views

Recipe for diced shark fin

How may the following shark-fin-shaped Goal distribution be cooked up with 44 ingredients in a roll recipe R based on the roll sum of two 6-sided dice with non-standard allotments of dots? Goal: ...
42
votes
1answer
1k views

The hardest crossword you'll do today!

This could well be the most difficult crossword you do today! Please note that the use of Google and other search engines is STRICTLY FORBIDDEN. (Of course, I have no way of policing this, but if ...
10
votes
6answers
616 views

A looped building with Prime rooms lighted

Imagine a building with 200 consecutive connected rooms as shown below. The shape is not important. It could be a circular loop building. You do not know the room numbers but you are told that they ...
5
votes
1answer
510 views

Some luck involved

Can you guess the theme? OK, feel free to reverse image search, it's been many days now. Slight Tip: Tip 1: Tip 2: Last Tip:
1
vote
1answer
177 views

Found this on The Ohio State University campus on a pillar relatively hidden from view. Any leads? I’m clueless

Here is the photo of the code... I think. I don’t know what it could be, but it was duct taped to a pillar for several weeks before I was kicked off campus from COVID-19:
12
votes
1answer
456 views

Humans, vampires and mirrors

Here is a room composed of $10 \times 10$ squared cells. Some cells contain a double-faced mirror ( / or \ ) that reflects the light with an angle of $90°$ on both sides. The other cells can be empty (...
11
votes
2answers
510 views

Mosaic by Albrecht Dürer

This is a visual puzzle (known as "mosaic" or "fill-a-pix") with the same rules as MineSweeper: The grid is to be filled with colored and white tessera. Choose whatever color you like for the colored ...
33
votes
1answer
3k views

MASTERING Sudoku

Fill the grid with letters M, A, S, T, E, R, I, N and G. Standard Sudoku rules apply. Additionally, the words on the right-hand side must appear in the given orientation (across/down). Each word ...
2
votes
1answer
110 views

Footmen And Friends #3: Eviction

Welcome to Episode 3, where we have a strange puzzle for today. Pawns aren't legally allowed on the first and eighth ranks, but today we make an exception for the sake of creating another long but fun ...
2
votes
1answer
128 views

Footmen And Friends #2: Leapfrog

Seeing as the pilot episode was a major success, with an outstanding and correct response from one of our viewers, it’s time for Episode 2. Remember, we show puzzles with kings and pawns only! Those ...
23
votes
4answers
3k views

A six letter body part

The question relates to a recent puzzle: One is outstanding, another doesn't belong : Says Grandpa Take the word PARENT for example. If you take 2 consecutive letters out, the remaining four ...
5
votes
1answer
177 views

Footmen And Friends #1: A Long Ways Away

Tonight premiers the first show of Footmen And Friends, a show dedicated exclusively to kings and pawns. Let's give these soul-men of chess a chance to shine instead of their big sisters and brothers! ...
9
votes
3answers
345 views

Where art thou, oh native rooks?

Here’s a tough puzzle for you all today! Given that both White and Black conspired to reach this position as briskly as possible, where standth White’s native rooks (the one from the starting ...
20
votes
1answer
1k views

Four mathematicians and their ages

Four mathematicians, none yet a centenarian, meet for coffee. The graph-theorist among them noticed that the common divisor graph of their ages (that is, the graph whose vertices are their ages, two ...
11
votes
5answers
2k views

Nice no-computers way to find limerick primes?

A limerick number is a 5-digit number whose digits are in the form of a limerick rhyme scheme: $aabba$. How many limerick primes (limerick numbers which are also prime) are there? The answer is ...
5
votes
1answer
163 views

Against the Grain, Salt to the Sea: Sudoku

Against the Grain, Grain of Salt, Salt to the Sea, Sea...badge? What Badge? Of course, guessing is not fun, right? Anyway, congratulations to anyone who get this! :D
6
votes
1answer
291 views

Just Another Sudoku for PSE

Crafted with love for PSE, <3
17
votes
4answers
2k views

Paint 21 Squares of a 7×7 Board Without Forming a Rectangle

Got a nice puzzle from my friend, when he was competing in IWYMIC/IMC 2011. Paint $21$ of the $49$ squares of a $7 \times 7$ board so that no four painted squares form the four corners of a rectangle....
3
votes
4answers
1k views

Series of interestingly increasing words!

What is the next word(more than one is possible!) in the below sequence of words: NO, ATE, OPTS, _ _ _ _ _ ? Note: 1 Only standard English words(as per Oxford English Dictionary) are to be ...
1
vote
5answers
454 views

Multiple XOR operations

Find $8$ distinct $8$-bit numbers, each with $4$ bits set to one, such that the cumulative XOR of these bytes is $10101010$. I imagine there are multiple answers, so the first correct answer wins the ...
4
votes
1answer
145 views

Another series of fortunate (and sideways) transpositions

Using only a sequence of transpositions, see if you can take this: to this: while maintaining English words on each of the three horizontals. At each step, you may transpose any two neighboring ...
14
votes
2answers
406 views

A series of fortunate transpositions

Using only a sequence of transpositions, see if you can take this: to this: while maintaining English words on each of the three horizontals. At each step, you may transpose any two neighboring ...
4
votes
1answer
218 views

Put the numbers $1, 2, …,16$ in circles

Put the numbers $1, 2, 3, ..., 16$ in circles so that the sum of the four numbers on each side of the triangle should be equal.
9
votes
1answer
294 views

A new year's mathematical mystery

Sam, Magnus, and Olivia each try to write the number 2020 as the sum of consecutive positive integers. They each use more than one integer, a different number of integers to the others, and none of ...
0
votes
0answers
328 views

A Logician's Game of UNO Flip

Two players are in the middle of an ongoing one-on-one game of UNO Flip, with all its standard rules in effect. Play is currently Light Side Up. It is Player B's turn. Player A has 3 cards remaining, ...
14
votes
2answers
1k views

Make a hexiamond star by hand

Using some or all of the hexiamonds (pictured), make a star. You may flip pieces. The usual tiling rules apply, no overlaps, no gaps. Use only one or none of each piece. Answer is unique. Target shape ...
6
votes
1answer
889 views

And another one bites the dust

I recently found an extraordinary moremover online today. Have fun finding the solution! It’s White to move and mate in 19 moves! Bonus: Explain the title in relation to the solution! Jozef Lozek, ...
5
votes
1answer
123 views

Sum of All the Others

There are ten different 10-digit decimal fractions, one of them being equal to the sum of the other nine. If each number has 10 unique digits, not counting the 0 before the decimal point (for example ...
0
votes
1answer
127 views

Confusing letter

I once received a letter where all letters of the alphabet was shuffled around. The task was then to find out what each letter was and then read the letter. I wrote a little letter for you: Be ...
-3
votes
1answer
480 views

123456789 = 100 with three operations? [duplicate]

Given the sequence 123456789 You can insert three operations (+,-,X,/) into this sequence to make the equation = 100. Is there a way to solve this without brute force?
7
votes
2answers
534 views

Pensive Nonogram - Two-Colour Puzzle

Fourth two-colour puzzle in the 32nd issue of Mega Pixel Puzzles by Puzzler.. I’ve made some progress, but I am stuck. Can you help me find my next move in it? (The puzzle is below)
7
votes
1answer
303 views

The Newest Cycle

A wonderful new chess problem has appeared lately that is most wonderful. I am here to share it with the world today. But you must solve it in order know about it’s glory! It’s White to move and ...
16
votes
3answers
3k views

Prime to Prime: Get all first 25 Prime Numbers using up to 4 Primes

The first 25 Prime Numbers are 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97 Using up to 4 prime numbers and the following mathematical operations, get all the 25 primes. + ...
9
votes
1answer
496 views

Twelve Labours - #12 Pluto Pups

This puzzle is part of the ‘Twelve Labours’ series, but can be solved independently. Previous instalments can be found here: Prologue | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 It was ...
3
votes
1answer
269 views

Rotary phone with numbers and letters

I am going to organise a quest for teenagers. I have a vintage phone like below: I am looking for ideas how to use the rotary phone with numbers 1,2, ..., 9, 0 and letters A, B, C, F, H, I, K, L, M, ...
8
votes
1answer
708 views

(Im)Possible 8-Puzzle

Can you solve this 8-puzzle in 16 moves or less?
12
votes
2answers
804 views

Hearts and Spades in a Row

From a deck of playing cards remove hearts ace to seven, and spades ace to seven. Now place them on a table in a row so that the number of cards between the two aces is 1, the number of cards ...
3
votes
2answers
338 views

What was Grandpa really doing?

"Guess what happened during my walk". Said Grandpa "I saw gods in a ghetto"! He continued with a smile. "What?" I said. "Well, not really. But can you guess what I did?", Grandpa asked. ...
4
votes
1answer
114 views

You Tell Me What To Choose

I found this nice problem in A.C. White’s 1912 book “The Theory Of Pawn Promotion” the other day. Enjoy! It’s White to move and checkmate Black in 5 moves, Don’t forget to explain the title! ...
2
votes
4answers
638 views

Grid Puzzle - Paint

A student was found making Graffiti in the teacher's office. He was punished and was asked to repaint the wall of the room. The teacher gave him a grid to show which part of the wall should be painted ...
10
votes
4answers
2k views

What's the most rewarding path?

Get from the top-left to the bottom-right using only right and down moves. Pick up as much gold as possible. There is only one maximum.
3
votes
2answers
242 views

Minesweeper puzzle - Too many twos

A Gobo is caught for leaving the school for the lnternet bar to play computer games without permission. He is asked to solve a problem. Put 4 mines in a 3 by 5 minesweeper grid to fill ALL the other ...
8
votes
2answers
335 views

Hand tiling puzzle demonstrating Eisenstein triple $c^2 = a^2 -ab + b^2$

An Eisenstein triple is related to 60 degree triangles and a special case of the cosine law. But we need not worry about that except to note that a specific example of an Eisenstein triple is $7^2 = 5^...

1 2 3
4
5
14