This tag is meant for questions about the mathematical principles behind games, riddles, or their possible solutions. If the answer is known to you please do not use this tag to "riddle" other users, but rather to ask about the correctness of a possible solution or ways to extend and improve an ...

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16
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0answers
247 views

What Rubik's Twist configuration has the lowest visible surface area?

The Rubik's Twist has been a fun time sink. From the wiki page, [It] is a toy with twenty-four wedges that are right isosceles triangular prisms. The wedges are connected by spring bolts, so that ...
0
votes
3answers
62 views

How is this true? Bookworm puzzle

This is from Eugene Northrop's book Riddles in Mathematics. Why is the answer 1 inch. Iit should be three. What logic am I missing here?
1
vote
1answer
47 views

Is the puzzle logically (or in some other way) correct?

There are 30 metereologists working in their laboratory making predictions about the weather for the next day. They say either "Tomorrow will be sunny" or "Tomorrow will be cloudy". One of the ...
1
vote
0answers
224 views

Snake cube puzzle equation

This is a Snake Cube Puzzle I am trying to understand the solution from mathematical point of view. Someone even wrote a solver: https://github.com/markfickett/snakepuzzle but I can't really read ...
0
votes
1answer
63 views

What question to ask to find right path

Suppose a certain country is inhabited by truth teller and liars, who only respond to yes or no questions. A tourist comes to a fork in the road where one branch leads to the capital, and the other ...
8
votes
2answers
138 views

Finding pattern

Just a puzzle. \begin{matrix} 2 & 9 & ? \\ 11 & 33 & 66 \\ 8 & 3 & 27 \\ \end{matrix} The options are $35$, $40$, $45$, $55$. $45$ is false. I ...
1
vote
2answers
57 views

Can you find the lighter and heavier marbles?

You have $10$ bags with marbles. Each bag has $2000$ marbles. Standard marbles weight $10$g. However, one bag has marbles that all weight $9$g and one bag has marbles that all weight $11$g. If you can ...
0
votes
1answer
38 views

Nontechnical Proof of “Puzzle on coins: Designing an operation”

Previously asked: A square table has a coin at each corner. Design an execution sequence, each of whose steps consists of one of the following operations: ONE (O): The operation ...
1
vote
3answers
2k views

Pattern-matching puzzle (shapes)

some puzzle that can be found online are typically a 3x3 grid where you've got nine spots filled with some images or symbols or geometric figures and you have to predict what the missing one should ...
-9
votes
2answers
732 views

?+?+?=30 (1,3,5,7,9,11,13,15) [duplicate]

?+?+?=30 Please slowe this question and reple answer
0
votes
0answers
69 views

find chair in survivor problem

Complete Question Text: Take a second to imagine that you are in a room with 100 chairs arranged in a circle. These chairs are numbered sequentially from One to One Hundred. At some point ...
2
votes
2answers
62 views

Shortest distance between two moving points

So I ofund this question on the internet, which turned out more tricky than I thought: " The position of boat A is given by $x(t)=3-t$ and $y(t)=2t-4$ The position of boat B is $x(t)=4-3t)$ and ...
33
votes
5answers
6k views

Chance of getting a date

A girl you like tells you that there's a $1$% chance she'll go out on a date with you. What is the expected number of times you have to ask her out before you get a date? (Not a homework problem - I ...
84
votes
17answers
15k views

How do you find the center of a circle with a pencil and a book?

Given a circle on a paper, and a pencil and a book. Can you find the center of the circle with the pencil and the book?
0
votes
5answers
8k views

Math Riddle in Combinatorics.

A blind man is on a strange island and he has 2 red pills and 2 white pills, completely identical and has kept in his pockets, he needs to take 1 red pill and 1 white pill order doesn't matter. If he ...
5
votes
14answers
2k views

Measure 11 liters using bottles of 16, 6, and 3 liters

This question has been bugging me for a day and finally I gave up and decided to ask the community for it so here's how it goes: Suppose we have 3 bottles with capacities of $16,6$ and $3$ liters, ...
1
vote
1answer
80 views

the blood test riddle (number theory)

A microbiologist has been given a set of $100$ blood vials. Exact one of those $100$ vials is positive to a concrete disease X. The microbiologist desires to send only $7$ vials for analysis. He can ...
38
votes
7answers
5k views

How many scientists can survive?

Yesterday the aliens took 100 scientists from Earth as prisoners. They want to test how smart the humans are. The aliens made 101 headbands, numbered from 1 to 101. On the contest day, they throw ...
5
votes
2answers
135 views

Optimal scheduling dilemma (A textbook math problem IRL)?

I am trying to solve a scheduling problem for a boys camp. I have 12 teams(A through L), 6 sports for them to play, and 6 periods for them to play in(P1 through P6). ...
0
votes
3answers
76 views

Verbal Reasoning (Puzzle)

There are four persons A, B, C and D. The total amount of money with A and B together is equal to the total amount of money with C and D together. But the total amount of money with B and D together ...
0
votes
4answers
66 views

How to come up with proofs of these results? Or, are these results true in the first place?

Let $x_n$ and $y_n$ be integer sequences determined by $$x_n + y_n \sqrt{2} = (1+\sqrt{2})^n \ \ \ \mbox{ for } \ n= 1, 2, 3, \ldots. $$ Then how to show that (a) $x_{n+1} = y_{n+1} + y_n$, $\ \ \ ...
0
votes
2answers
60 views

Find minimum and maximum wins required in a $8$ team tournament

In a tournament, there are $8$ teams in total and playing against each other $2$ times. We need to find (-)What is the minimum no of wins required to qualify for the next round? (-)What is the ...
0
votes
0answers
39 views

Formula for coefficient of Mahonian numbers

I recently came out with this article . It tells about triangle of mahonian number.The T(n,k) is coefficients in expansion of Product_{i=0..n-1} (1 + x + ... + x^i), where k ranges from 0 to n*(n + ...
2
votes
3answers
320 views

Is it possible to solve the Zebra Puzzle/Einstein's Riddle using pure math?

A coworker of mine posted a problem in our local communication software that seems to be a simpler variation of the Zebra Puzzle/Einstein's Riddle. I know how to solve it intuitively, by using ...
1
vote
1answer
96 views

Cutting chocolate diagonally

Given is chocolate with rectangular pieces of size $a \times b$. If cut diagonally, how many pieces will it be split into? If knife passes exactly by co-catenating we assume there is no damage to ...
1
vote
1answer
53 views

KenKen puzzles. Minimum number of “clues” to uniquely define nxn grid.

I recently discovered the "KenKen" puzzle and have been trying to figure out some of the mathematics behind it. This led me to the following question: Given an N x N grid, what is the minimum number ...
0
votes
1answer
512 views

Propositional Logic “Riddle/Puzzle”

I have this kind of 'riddle' as a question that i need to complete, however I'm not sure what to do of it. This is the question: ...
1
vote
1answer
81 views

A simple to explain solution to this kids' geometry puzzle

A smart 10 year old asked me basically this question. Consider a rectangle with both diagonals drawn in. Now ask if you can visit all the edges by travelling from some starting vertex and only ...
0
votes
1answer
444 views

Riddle: Minimum time to cross the bridge?

I've recently been asked to solve a riddle, which sounds something like that: There are 4 people on the one side of the bridge. They have only 1 flashlight. It takes respectively 1, 2, 5 and 10 ...
5
votes
1answer
153 views

Time and distance: Police and a thief with a twist.

A thief was given a head-start of 15 hour. The velocity of the thief being 4 km/hr and the police chasing after him be 5 Km/hr. A dog is moving to and fro between the police and the thief, starting ...
1
vote
1answer
771 views

Lexicographical rank of a string with duplicate characters

Given a string,you can find the lexicographic rank of a string using this algorithm: Let the given string be “STRING”. In the input string, ‘S’ is the first character. There are total 6 characters ...
0
votes
1answer
51 views

Mini Tetris Winning Configuration

So here's the problem: A winning configuration in the game of Mini-Tetris is a complete tiling of a 2 x n board using only the three shapes shown in Figure 1. By allowing rotations, there can be ...
4
votes
1answer
117 views

In the card came “Projective Set”, show that 7 cards do always contain a set. [duplicate]

In the game of Projective Set, it turns out that any seven cards contain a projective set. How can one prove this? And for fewer than 7 cards, how can we determine the probability that one or more ...
0
votes
2answers
91 views

In the card game “Projective Set”: Compute the probability that $n$ cards contain a set

In the game of Projective Set, it turns out that any seven cards contain a projective set. For fewer than 7 cards, how can we determine the probability that one or more sets exist (in terms of the ...
1
vote
1answer
81 views

What is the optimal investing solution for the given simulated market?

I have come across an artificial, simulated, stock-market type of situation, whose rules, I find, create a rather interesting problem. I want to know if there is a mathematically optimal solution for ...
0
votes
2answers
114 views

Finding the minimum wins in a round-robin tournament.

There are 16 teams in total. They are divided into two groups of 8 each. In a group, each team plays a single match against every other team. At the end of the round, top 4 teams go through to the ...
2
votes
1answer
84 views

What is the _simplest_ way to solve problems of this kind?

Two doors with talking doorknockers - one always tells the truth and one always lies. One door leads to death other to escape. Only one question may be asked to either of the door knockers. What would ...
1
vote
0answers
85 views

Real Mathematics in Video Games

Out of curiousity (and perhaps also to amuse my students), I am looking for examples of actual mathematics appearing in video (computer) games. Of course that sort of mathematics would probably be ...
2
votes
3answers
56 views

Number in tens place

A number in tens place in result of $4^{2015} \cdot 9^{2016}$ is? Obviously without using calculator, though I doubt it could count with those high numbers. By tens place I mean, for example if you ...
1
vote
2answers
49 views

Number of boys in school

We have $400$ students in a school. Every $20^{th}$ student failed at the end of the school year. Which was $2\%$ of schools girls and $10\%$ of schools boys. The number of all boys attending the ...
1
vote
2answers
77 views

Number addition riddle

I got this math "riddle" in one of my math test, and I would love to know how to solve it. If $$S = 1 + 2 + 3 + 4 + \ldots + 2015,$$ then a sum of $$1 + 2 + 3 + \ldots + 2015 + 2016 + \ldots + 4030$$ ...
1
vote
1answer
60 views

Number of apples in a basket riddle

You have six baskets with apples - 10,12,15,20,22,25 (this is how many apples there were in them - 10 in first, 12 in second..). Some of the apples are red and some are green. After one basket was ...
2
votes
1answer
48 views

Market Making Card Bet Game

In an interview I received the follow question: We have 3 cards face down, and we give each card in a deck of 52 a numeric score ( A = 1, 2=2, .... , J=11, Q=12, K = 13). The interviewer asked me to ...
1
vote
1answer
82 views

Minimising the distance covered

I am trying to solve the question: You are trying to get to go from A to B 10 times. At each journey, a coin is flipped and if its heads, a wall appears in the middle as in scenario 2. If tails, no ...
2
votes
2answers
103 views

How to find the minimum expression(s) of a set of fixed-width bit fields?

If we define $x_1 x_2 \cdots x_n$ as a bit field of width $n$, and each element $x_i$ may be $0$, $1$, or wildcard $*$. A set of 4-width bit fields $\{0000, 0001, 0100, 0101\}$ can be aggregated ...
0
votes
1answer
60 views

If the letters T*(RBJBR)=VPLNT each represented a unique digit, and “RBJBR” was a five digit number, what are possible values for the letters?

If the letters T*(RBJBR)=VPLNT each represented a unique digit, and "RBJBR" was a five digit number, what are possible values for the letters? (Or ONE possible value.) Can we do this in a way that ...
81
votes
18answers
8k views

Fastest way to meet, without communication, on a sphere?

I was puzzled by a question my colleague asked me, and now seeking your help. Suppose you and your friend* end up on a big sphere. There are no visual cues on where on the sphere you both are, and ...
2
votes
2answers
414 views

Mathematics riddle

The question is as follows: You are taking part in a treasure hunt, where the directions to finding the treasure are given using cryptic clues. You start at a cross-roads, with roads heading out ...
2
votes
1answer
90 views

Palindromes on a digital clock [closed]

A palindrome is a number that reads the same forwards and backwards,such as $55$ and $12321$. How many times in a $24$-hour period of time on a digital clock does the number reveal a palindrome?
0
votes
1answer
53 views

Rectangles in a figure

I have this figure and I have to find $5$ rectangles (which includes squares). I just see four. Where is the $5^{th}$ rectangle?