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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
88 views

14sums - the diamond standard

My initial question had lots of answers, and my second had too many constraints. So, I have removed some constraints and added another. Same rules as before, but we are now using $[0,6]\cap\mathbb{Z}$....
1
vote
1answer
340 views

Will two kangaroos ever meet after making same number of jumps?

There are two kangaroos on an x-axis ready to jump in the positive direction (i.e, toward positive infinity). The first kangaroo starts at location $x_1$ and moves at a rate of $v_1$ meters per jump. ...
4
votes
2answers
132 views

Probability in Fighting Tournament in which Contestants consume each other

A tournament has 2 teams of 24 people each of weight 1. Each team sends one person into the pit where they fight until one consumes the other taking on all their weight. The probability that one ...
5
votes
1answer
109 views

21sums - more constraints

My initial question had lots of answers, as we can practically choose the middle square to be anything we want, and work outwards to the exterior edges, with the corners providing the flexibility ...
6
votes
7answers
1k views

9sums - a logical deduction puzzle

Each set of minuses contains an integer in the range [1,5]. The given numbers are the sum of the surrounding 4 numbers. --- --- --- --- 13 14 11 --- --- --- --- 11 ...
4
votes
2answers
141 views

Finding both fake coins in a set of $5$

There are $5$ rupees on Arnav's table. He knows that exactly $2$ of the rupees are counterfeit. One of these $2$ coins is lighter than a normal (non-counterfeit) rupee, and one of these $2$ coins is ...
2
votes
3answers
223 views

Infinitely many stacks of infinitely many cards on infinitely many tables

You are trapped in a room. In front of you, there is a table on which there is an infinite number of stacks of cards each containing an infinite number of black or white cards. Two stacks are ...
7
votes
5answers
379 views

Cutting a Slice of Cake Into Two

Driven out of a serious question, when sharing a slice of cake in a coffee shop how can my two friends split it without going down the middle (the cake is likely to crumble if you do this!) Given a ...
5
votes
1answer
99 views

Shortest path for delivering packages [duplicate]

A version of the Travelling Salesman Problem, but with certain points. We are talking about a town where 8 canals run from the middle boathouse into the city. You can only travel one way on the green ...
0
votes
1answer
69 views

What is the area of the shaded region? (Overlapping areas) [closed]

What is the area of the region poly1 formed by the arcs 'cdke'. The square is of sides 10 units long. The region poly1 is formed by four overlapping quadrants.
7
votes
3answers
521 views

Three Visual Puzzles

I'm designing a puzzle game, and am trying to play-test some concepts. Can you solve these? 108153767833 = A + B + C. What are the components and why? Note for C: As a hint to correct an oversight, ...
4
votes
2answers
174 views

The bottle(s) of pills of a different weight

I am a laboratory man dealing with random medicine. Day 1 I have 10 bottles of pills. 9 of them contain good pills that weigh 1.000g each, and the other one contains bad pills that weigh 0.999g each....
6
votes
3answers
767 views

Gaby and Jack's Number Guessing Game

Gaby, a good mathematician, thinks of a whole number between 1 and 100 inclusive. What is the least number of questions Jack needs to ask her, and what questions should those be, if he is to work out ...
1
vote
2answers
301 views

What is the next number in the given series?

I know that next number questions are not popular here, but this one is tough and I couldn't figure out the pattern. To give an idea one of the questions had a pattern of Prime(Fib(n)). So this is ...
3
votes
1answer
147 views

Three-digit multiplication puzzle, part III: Return of the Hex

Followup to: Three-digit multiplication puzzle and Three-digit multiplication puzzle, part II: ever heard of senary? Place different three-digit hexadecimal numbers (000-FFF) on each of the seven ...
-3
votes
2answers
198 views

Brain Testing Logical Reasoning Puzzle

Can you answer this logical puzzle? Puzzle Source: https://www.funwithpuzzles.com/2018/12/brain-testing-logical-reasoning-puzzle.html
3
votes
2answers
136 views

Three-digit multiplication puzzle, part II: ever heard of senary?

Followup to: Three-digit multiplication puzzle I'd never heard of "senary" either, until creating this series of three puzzles. It seems that "senary" is the word for base-six notation. Who knew? ...
16
votes
2answers
2k views

Blind Person Ball Game

You are blind and your friend presents you with 6 equal balls of which 3 are red and 3 are green. You friend challenges you to game to find a green ball. You must select 3 of the balls and your friend ...
4
votes
1answer
179 views

Three-digit multiplication puzzle

Place different three-digit numbers (000-999) on each of the seven nodes of the following diagram: There are six lines in the diagram, on each of which are three of the nodes. On each of those lines, ...
4
votes
1answer
208 views

The Housing Estate

A constructor wishes to build a housing estate in a square terrain with 64 (8 x 8) smaller plots of land, at most one house to a plot. Local urban rules allow building a house in a plot only if at ...
-1
votes
3answers
113 views

Which number is missing from the bottom grid? [closed]

It's a hard puzzle, can you find the missing number?
-5
votes
2answers
71 views

MATH PUZZLE ABOUT SEQUENCE [closed]

In the array of numbers below, each number above the bottom row is equal to three times the number immediately below it. What is the value of x+y? ...
7
votes
1answer
470 views

Fourteen numbers around a circle

Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
12
votes
3answers
758 views

The Mxied Atdiiodn

It has been swohn that to raed a txet the oedrr in which the lrtetes of each idniaduvl word aepapr is not ipmotanrt, so lnog as the fsrit and lsat ltetres are the correct oens. This is not the case ...
7
votes
2answers
557 views

Primes and Squares

Place a different prime or square number on each of the fifteen disks below so that the number in any disk that lies on two others is the sum of the numbers in those disks. Do so in such a way that ...
0
votes
1answer
106 views

A Colorful Honeycomb

What strategy can you use to color using only 6 colors the lines in an infinite hexagonal tiling such that no two sides of the same hexagon have the same color?
8
votes
2answers
631 views

Four Magic Ellipses

These four ellipses represent four sets and all the possible ways they can intersect (a Venn diagram, in other words). There are 8 regions inside each ellipse, and 15 regions altogether. Is it ...
61
votes
15answers
9k views

2 Monkeys on a computer [closed]

(a) Two monkeys are typing capital letters (A-Z) randomly. The first stops typing when the word COCONUT appears as seven successive letters. The second stops typing when TUNOCOC appears; TUNOCOC is ...
8
votes
2answers
180 views

What is the largest number of cubes that can be cut?

Consider a cube made up of 27 unit cubes. If you consider a plane going through the middle of the larger cube it cuts through a number of the unit cubes. The number of cubes that are cut depends on ...
1
vote
1answer
122 views

Garden Variety Family

Some siblings* were discussing the unique mathematical qualities of their respective ages the other day, and they determined that at one point in history, the following equations were true. $\hskip ...
6
votes
2answers
270 views

The Magic Letter H

Place seven different positive integers on the empty disks of the H figure below so that the product of the three numbers in any straight black line is always the same. Now place seven other numbers ...
8
votes
3answers
2k views

FBI number riddle

A friend sent me this riddle and I can't figure out a solution: January = 251017 February = 25628 March = 81335 April = 12145 May = 251353 June = 51064 July = 251074 August = 20186 ...
14
votes
5answers
1k views

When did I make this puzzle?

I was flipping through some of my old puzzling notebooks, and I found an old puzzle of mine I don't quite remember. I tried to find when I made it (I put the date I made all of my puzzles on them), ...
6
votes
2answers
192 views

Numbered Billiard Balls

Ten billiard balls are stacked in the form of a regular tetrahedron, six in the bottom layer, three in the middle layer, and one in the top layer or cuspid. All the balls are numbered (with positive ...
-1
votes
3answers
101 views

Guess Me riddle #3

View the last part here Guess the word Sir, I bear a rhyme excelling In mystic force and magic spelling Celestial sprites elucidate All my own striving can't relate What am I?
7
votes
1answer
152 views

A Christmas Tennis Tournament

Three friends, Charles, Hugh, and Freddy, played a one-month tennis tournament, just one match between two of them every single day during last December. During the tournament, whoever lost the day's ...
8
votes
4answers
510 views

Maxit negotiations

Your military junta has recently overthrown the government of Malta and taken control of the small island nation. As a way to finance your wise and just dictatorship, you have decided to threaten the ...
3
votes
2answers
185 views

This title is not a clue

$\color{#FFFFFF}{\textsf{I am required to have text in my question. This is not a clue. Stop reading and look at the image.}}$
4
votes
2answers
188 views

Input/Output Problem #7

See here for basic rules on problem. Input/Output Problem #1 Problem #7 Make an optimal machine that accepts sequences of integer digits 1-4 such that each triplet contains three different numbers. ...
3
votes
2answers
108 views

Input/Output Problem #6

See here for basic rules on problem. Input/Output Problem #1 Problem #6 Make an optimal machine that accepts sequences of integer digits 1-4 such that all 1s are at the beginning and all 4s are at ...
4
votes
3answers
166 views

Input/Output Problem #5

See here for basic rules on problem. Input/Output Problem #1 Problem #5 Make an optimal machine that accepts sequences of Rock Paper Scissors games where first input is Player 1 and second input is ...
4
votes
2answers
159 views

Input/Output Problem #4

See here for basic rules on problem. Input/Output Problem #1 Problem #4 Make an optimal machine that accepts sequences of digits 1-3 that contain a 1,2,3 in each triple of numbers and has no ...
3
votes
1answer
110 views

Input/Output Problem #3

See here for basic rules on problem. Input/Output Problem #1 Problem #3 Make a machine that accepts sequences of digits from 1-4 that have a product that is a square number.
5
votes
8answers
476 views

Input/Output Problem #2

See here for basic rules on problem. Input/Output Problem #1 Problem #2 Make an optimal machine that accepts any letter combination that begins with a consonant and alternates vowel consonant from ...
12
votes
3answers
859 views

Input/Output Problem #1

The basis for this problem is that you did to make an optimal pattern so that all inputted sequences will be "accepted" if they fit the rules of the problem and "rejected" if they break any of them. ...
0
votes
2answers
92 views

How many bulbs are switched on? [duplicate]

I remember this one from an interview: There is a room with 100 light bulbs (numbered from 1 to 100) lined up in a row. All the bulbs are off. 100 people are lined up in front of the room. The ...
5
votes
4answers
252 views

Recursive Doors and Deluders Puzzle

You start off with $\$1.$ You are faced with $20$ doors, and in front of $10$ each are lying lookouts and honest guards. If you enter and completely walk through a door guarded by an honest hombre, ...
4
votes
0answers
191 views

Which Number Replaces the Question Mark?

Can you find out what the numbers below have in common? Can you figure out what comes next? ...
3
votes
2answers
321 views

Assets Split Puzzle

An old woman had the following assets: ...
1
vote
3answers
201 views

What is the 10-digit combination of Sherlock's locker?

Sherlock made an elaborate code to remember the 10-digit combination to his locker. This is the code he came up with: A-K-B-J-C-H-D-G-E-F Each letter stands for a single digit number (0-9) When two ...