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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3
votes
4answers
220 views

logic puzzle (truth-tellers / liars)

I am trying to solve this puzzle. It is supposed to be solvable. There are 3 people A,B,C. One of them is always lying, one of them is always telling the truth and one of them is always answering ...
2
votes
0answers
90 views

ZELDA Guardian Puzzle Part II - Shortest Path (Unsolved for new rules)

This question is in relation to the following previously asked question: Twilight Zelda Guardian Puzzle : Shortest Path (UPDATE: ADDED RULES) A 1-step-less solution was uncovered, but under an ...
1
vote
3answers
308 views

Find a possible pair of numbers given HCF and a factor of the LCM

I was just going through a GCSE paper with a student and I came across a question that I'm struggling to find a good method for. The question was this: Martin thinks of two numbers. The ...
-1
votes
2answers
162 views

A mathematical puzzle [closed]

I am given a set $S$ of sorted numbers and I have to find value of $rndm(S)$ $$\Large rndm(S)=\sum_{s\text{ is a subset of }S}\max(s)-\min(s)$$ Where $\max(s)$ represents the maximum value in set ...
2
votes
4answers
161 views

Logical puzzle. 3 Persons, each 2 statements, 1 lie, 1 true

I got a question at university which I cannot solve. We are currently working on RSA encryption and I'm not sure what that has to do with the question. Maybe I miss something. Anyway, here is the ...
0
votes
3answers
65 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
49 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 ...
0
votes
1answer
67 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 ...
1
vote
2answers
59 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
42 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 ...
0
votes
0answers
78 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
193 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 ...
-9
votes
2answers
847 views

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

?+?+?=30 Please slowe this question and reple answer
16
votes
0answers
261 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 ...
1
vote
1answer
90 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 ...
8
votes
2answers
139 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 ...
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, ...
0
votes
4answers
68 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) $x_{n+1} = y_{n+1} + y_n$, $\ \ \ ...
5
votes
2answers
137 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
2answers
67 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 ...
11
votes
2answers
320 views

Twilight Zelda Guardian Puzzle : Shortest Path (UPDATE: ADDED RULES)

I'm playing a video game right now and in it is a puzzle (see here). There are solutions to solving it (see here) on the Internet, but I'd like to know if this path is the shortest path (least amount ...
0
votes
0answers
44 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 + ...
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 ...
1
vote
1answer
58 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
3answers
78 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 ...
2
votes
3answers
363 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
84 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 ...
5
votes
1answer
175 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 ...
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 ...
0
votes
2answers
94 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 ...
4
votes
1answer
119 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 ...
1
vote
0answers
89 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
59 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 ...
2
votes
1answer
85 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
2answers
50 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
82 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
64 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
62 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
49k views

What three odd integers have a sum of 30? [duplicate]

I've been asked the following question: What three odd integers from the set {1,3,5,7,9,11,13,15} that when summed together equals to 30? Note that any integer can be used more than once. Is there ...
1
vote
1answer
84 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 ...
0
votes
2answers
134 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 ...
3
votes
1answer
101 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?
6
votes
0answers
96 views

Fastest way to meet, without communication, in a toroidal palace?

I was interested by a similar question asked here, but wanted to pose a slightly different variant that avoids some of the pitfalls and ambiguities in the first question in order to ask something more ...
5
votes
2answers
88 views

If $\sum_{i=1}^n a_n=0$ then you can find a “good” ordering of $a_i$.

I'm trying to prove (or disprove, but I think it's true and I'll be surprised if someone would manage to disprove it) a small theorem. Given an array of real numbers $A=[a_1,a_2,...,a_n]$ such that ...
8
votes
1answer
275 views

Here is a riddle that I have no idea how to solve.

Okay, so I was trying to solve this riddle found here. It is a diagram of a star with 16 points. Each point corresponds uniquely to a number between 1 and 16. The letters on each point represent a ...
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 ...
0
votes
1answer
27 views

Deriving a function based on a relation/characteristic

Say I give you an integer set [1, N], which is the initial step, and define a notion of a step by this example: given N=16 ...
0
votes
1answer
60 views

Pick a random integer $x\in[1,N]$ and guess the value of $N$

$N$ people arrive at a concert, with tickets numbered $1$ to $N$. At the entrance, they all throw their tickets to a nearby trash can. You pull out a ticket with some number $x$ written on it. ...
2
votes
2answers
98 views

show that at least 3 balls have same weight

You are given 49 balls of colour red, black and white. It is known that, for any 5 balls of the same colour, there exist at least two among them possessing the same weight. The 49 balls are ...