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Questions tagged [mathematics]

A puzzle strongly related to mathematical facts and objects, or whose solution needs serious mathematical arguments. General mathematics questions are off-topic but can be asked on Mathematics Stack Exchange.

2
votes
1answer
27 views

Finding a path on an n x n grid, top left corner to bottom right corner, where n is even?

Given a puzzle of the following form: Find a path between the top left corner to the bottom right corner, visiting each spot (.) exactly once. You can only move horizontally or vertically. ...
10
votes
3answers
735 views

Greedy Chocolate Eaters

Alicia and Bobby play a game with a rectangular chocolate bar, scored into an $m$ by $n$ grid of squares. The children alternate turns, with Alicia going first. On a child's turn, they must break ...
5
votes
2answers
148 views

Rotating 12 players on 2 tables

I'm stuck trying to find a good way to rotate 12 poker players on 2 tables. Assumptions: There are 12 players There are 2 tables We play for 4 hours Playing with sb means sitting at the same table ...
15
votes
2answers
374 views

What is the optimal strategy for this triangular board game?

I saw a board game somewhere and I want to know the optimal strategy for it. The game is played on a triangular board with 21 slots: The two players, red and blue, take turns to put numbered circles ...
6
votes
2answers
424 views

2019 is coming!

Use $2$ $0$ $1 $ and $9$ to make the numbers $66, 74, 76, and$ $77$ RULES You must use all 4 digits. Only the digits 2, 0, 1, and 9 can be used. You can make multi-digit numbers out of the numbers. ...
9
votes
0answers
218 views

Peaceful Encampments

This math puzzle is due to Donald Knuth (as far as I know; maybe he got it from someone else) circa 2014. Consider a plain represented by the unit square. On this plain we want to “peacefully ...
3
votes
1answer
118 views

need help in solving that numerical sequence

Sequence: 2, 3, ?, 8, 6, 7, 6, 5, 9, 3, ?, 1 I've tried to figure out what number I should replace to the *?*I have initially thought that was a modified fibonacci sequence example: we start with 2+3=...
6
votes
4answers
318 views

Soar High for You? No Way!

Me and my fellows upon a time, Have earned the championship in our prime. Alas! That time has passed, my dearest fren', But we are still often used, according to Ben. Soar high for ...
7
votes
1answer
144 views

Three stubborn siblings

2560147913 Three stubborn siblings, of which only one is whole, making history is their goal. What word am I looking for?
2
votes
3answers
1k views

A logic based word puzzle: Coins in a dark room

You are in an absolutely dark room, with (a large number of) coins strewn all over the floor. You know that exactly 20 coins are tails up. You need to split the coins into two groups, such that both ...
8
votes
8answers
987 views

What mysterious whole number am I?

From my second point of view I copy that amount of first. I am the dominant side of two but for many I'm the worst. I'll be tricky to find but today might be your day, after all my neighbour is 2/3 of ...
1
vote
2answers
124 views

What is the secret of this Math(s) “joke”? [closed]

On a page called 14 jokes only intellectuals will really understand, it lists: A mathematician is heading to a house party. Just as he is coming up to the house, he notices there are no cars parked ...
9
votes
3answers
253 views

The END (Riley riddle)

My prefix you say in astonishment, My infix within the prefix slightly smaller than a pie My suffix is huge, or even enormous, And here comes the end of the riddle. Hint 1:
9
votes
5answers
209 views

What's for dessert?

Another puzzle, yay! What do I want for dessert? An element, a blue liquid you breathe. The end of a sentence. wgpz tzggjr wgvxf bmzzi mzy It's three til' 4, plus forty more. Hint:
12
votes
4answers
592 views

A Chwistmas Widdle With a Twist

Chwistmas is the same with or without me, though I do wish you all Mewwy Chwistmas... I wish to be wid of my condition I am named and famed with humiliation A small happy square wheel! ...
10
votes
2answers
1k views

All neighbor sum is 0 on a chessboard

Neighbor cells of a matrix are defined as all the cells that share a common edge. A matrix is formed by putting real numbers in each cell. Form an $8 \times 8$ matrix (like a chessboard) where sum of ...
-4
votes
0answers
105 views

mathemathical-logical sequence solving

I need help in solving this sequence: 24, 333333, ?, ?, 53, 44444444, 82, ?, ?, 222244444444, ?, ?, ?, 444433333322221 reposting this because I wanted to add more informations. Now by taking a look ...
-4
votes
0answers
113 views

Numerical sequence

That's my last post for the week, I need help in solving this numerical sequence: ?, 36, 36, 18, 16, 14, ? I don't see any correlation between these numbers. Source:http://zagaza.ru/za548.htm ...
1
vote
2answers
145 views

Number sequence solving

Help me solving this sequence: need help 9,?,342,675,1230, ?,3561,5892 Source: http://zagaza.ru/za548.htm
1
vote
1answer
133 views

Sequence solving

I need help to find the x: 6 3412 x 8605648 I've noticed that the end doubles everytime so we have 6 then 12, then we should have 24 then 48 , I have also noticed that the first 2 numbers ...
5
votes
6answers
259 views

2019 to every day of the month

The grumpy professor looked at his class and said - ok so now it is 2019 can you use the four digits individually with *, +, -, /, ^ (raise to the power of) and ! to make each day of the month? You ...
13
votes
3answers
1k views

Spider and fly on a cube

A spider and a fly play a game with a cube of side length $s=1$ and with a positive real number $d$. First, the spider picks its starting point $S$ somewhere on the surface of the cube. Then the fly ...
7
votes
2answers
160 views

Which number goes in the square with the question mark?

My friend, who loves puzzles as much as me, gave me this image this afternoon. My friend game me a hint: Skyscraper, which, as Daniel Mathias pointed out in the comments, is a type of grid puzzle.
4
votes
1answer
198 views

This picture has some hidden message. What is it?

This picture was uploaded for the Olympiads of Medicine, from Porto. While the answer might be in portuguese, I don't find it likely. I tried some Caesar Cyphers, I assumed the colours represented ...
1
vote
1answer
130 views

Solve this sequence -pattern

Ok,I need to find the solution to this sequence: 1.(09), 1.(4), 2, 3, ?, 17 the number in parentesis is an infinite decimal like 1,099999 or in the second one 1,4444444,but i can't find an answer for ...
13
votes
2answers
693 views

Digit sums of successive integers

For a natural number $x$ both, the digit sum of $x$ and the digit sum of $x+1$ are multiples of $7$. What is the smallest possible $x$?
12
votes
9answers
22k views

The coach, the shoes and the whistle

I recently received the following mathematical puzzle in a Whatsapp group: After a lot of debating, the group got to the conclusion that the answer was I however, was skeptical. After a while I ...
-5
votes
0answers
57 views

2,0,1,9 New Year Digit Game Number 51,52, and 98 [duplicate]

I found every sum from 1-100 using 2,0,1,9 except 51,52, and 98. Does anyone have the solutions? It would be greatly appreciated if you could share them. Rules: All four digits must be used in each ...
-2
votes
2answers
101 views

Make 'b' the subject in the quadratic formula [closed]

Solve for b in terms of a,x and c in the fastest way possible.
2
votes
2answers
346 views

Can the sum, difference and product of 2 numbers be perfect squares? [closed]

If we take 2 numbers $x$ and $y$ such that $x>y>0$ and , can $x + y$, $x - y$ and $xy$ all be perfect squares?
3
votes
2answers
75 views

Can you have the harmonic, geometric, arithmetic and quadratic mean of 2 numbers all being integers? [closed]

I created this problem looking at the hm-gm-am-qm inequality (hm = $\frac{2xy}{x + y}$, gm = $\sqrt{xy}$, am = $\frac{x + y}{2}$, qm = $\sqrt{\frac{x^2 + y^2}{2}}$ and hm $\le$ gm $\le$ am $\le$ qm). ...
5
votes
3answers
405 views

My Grandpa's Box #1

My grandpa died last month. At the reading of his will, he left me a strange wooden box. A post-it-note on the side read "You were always good at puzzles." There was a number lock on the front that ...
0
votes
4answers
10k views

10 9 8 7 6 5 4 3 2 1 = 2018

Add the four basic operators × ÷ + −: 10 9 8 7 6 5 4 3 2 1 to get the total 2018. Keep the order; do not combine numbers. Don't use any brackets. Use all four operators at least once.
9
votes
1answer
298 views

The Lazy Laser Physicist: Part 2

The Lazy Laser Physicist is quite shocked about what happened to his setup over night: Almost all of his mirrors were taken away, but some other things have been put on his table. Besides these there ...
1
vote
2answers
96 views

Funny Business, Math Problem [closed]

The population of Humorville is 9,800 people. In this town, jokes travel fast. In one hour, each person who hears a joke tells three other people who have not heard it and tells no one else. Last ...
12
votes
3answers
1k views

The thought of my prefix brings many a smile; My infix is, mathematically

Here's my first attempt at a Riley! Good luck! The thought of my prefix brings many a smile; Sit down, relax, or sleep for a while. My infix is, mathematically; One point six times ...
10
votes
2answers
545 views

A differential equation with a hidden sentence

Find the specialized solution of $H''(r)-aH'(r)=0$ that satisfies $H'(0) = \frac{1}{p^2}$ and $H(0) = \frac{H'(0)}{a}(1+\frac{N}{Y}e^w)$ The question: Solve the above mathematic question Rewrite ...
13
votes
3answers
648 views

Simple Maths Riddle 5

Here's a special one for you! I am prime, I am composite Sum my digits and half; I'll be perfect! Don't multiply them, I won't yield a thing But don't worry, it's only the beginning! ...
2
votes
0answers
84 views

Write $\sqrt{5}$ as sums of powers of $1 + \sqrt{2}$? [closed]

The number $A = 1 + \sqrt{2}$ solve the equation $A^2 = 1 + 2 \sqrt{2} + 2 = 1+2A$. We also have that $$0 < \dots < A^{-2} < A^{-1} < 1 < A < A^2 < \dots $$ The powers are in ...
16
votes
1answer
475 views

To solve a simple heist

It happened by chance really. I was walking out from the bank when a man ran into me while rushing out. During our collision a piece of paper fell from his pocket. I quickly picked it up and tried ...
20
votes
1answer
1k views

What did I do yesterday Rebus?

What did I do yesterday ? Above image is the rebus. Src : slightly copied .
7
votes
1answer
234 views

Simple Maths Riddle 3

My counterpart has committed multiple crimes; Square us and add: the result is not prime. You use me for a reason; I'm not liked by Cartesians; My converse is a measurement of ...
1
vote
2answers
189 views

Simple Maths Riddle 4

I cheer, I shout, I scream My growth is too extreme I'm way too vast Rates too fast Continuity can only be my dream. What am I?
4
votes
1answer
448 views

Generalisation of Nim

I'm asking for a general formula/algorithm that can be used in such a game. There are $n$ piles, with varying number of pebbles. The number of pebbles in each pile is given by an array from $pile[...
16
votes
3answers
2k views

A clock where the hour and minute hands are the same length

Your buddy Frankie sold you a shoddy clock: it keeps good time, but the minute and hour hands look exactly the same! Both of these hands move continuously, and there is no second hand. How many times ...
18
votes
2answers
2k views

A strange computer programming language

Here is a list of rational numbers: $\frac{22}{21}, \frac{7}{11}, \frac{13}{7}, \frac{51}{65}, \frac{13}{17}, \frac{1}{13}, \frac{15}{2}, \frac{7}{1}$ This list is actually a computer program! It ...
3
votes
3answers
1k views

Three coins for the fair king [duplicate]

Based on the question Eight coins for the fair king: I saw a comment saying "There isn't a good solution known even with three coins in all cases". So the challenge here is to try to solve the same ...
45
votes
6answers
3k views

Eight coins for the fair king

You are responsible for creating new types of coins for the court. King respects the forgetful: he wants you to create 8 coins of different value, no more. King respects the feeble: he wants that any ...
6
votes
3answers
1k views

Different Ball Puzzle

You are working in a ball factory, where balls of weight 1U, 2U, 3U ... 8U are made in 8 sections. One day, you are given 1023 black balls , all (except one special ball) from section 1, meaning ...
3
votes
4answers
405 views

What will be the next term in this mathematical sequence?

What will be next in this series? $$0, 6, 24, 60, 120, 210, ...$$ I've tried it and noticed that the numbers are multiples of six. But I couldn't make a relation between them.