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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Best Math to learn for logic problems?

I have a friend who can do any Math logic puzzle in a few seconds. The ones where they ask about for e.g. the one with monkey and coconuts or guys at the bar taking and giving each other change. A ...
1
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2answers
45 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 ...
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1answer
30 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 ...
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0answers
31 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 ...
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2answers
31 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 ...
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2answers
101 views

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

?+?+?=30 Please slowe this question and reple answer
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0answers
92 views
+50

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
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1answer
52 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 ...
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2answers
53 views

mathematical calculation problems [closed]

I have been given the odd numbers $1, 3, 5, 7, 9, 11, 13, 15$ with the challenge of selecting any 3 numbers from the above, to produce the number $30$. We can perform any operation on numbers and ...
9
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2answers
115 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 ...
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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
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4answers
61 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
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2answers
109 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). ...
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0answers
58 views

A simple arithmetic puzzle [closed]

$_+_+_=30$ You can use the numbers $1,3,5,7,9,11,13,15$ to fill the gaps.
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2answers
37 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 ...
10
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1answer
223 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 ...
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0answers
25 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 + ...
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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
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1answer
25 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
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3answers
57 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
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3answers
196 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
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1answer
44 views

How to check if the 1st player can always win [closed]

Suppose $2$ people start with a pile of $n$ matches, and each turn each player takes $1$ to $6$ matches from the pile. The player to take the last match wins. Let $n=75$. Can the 1st player always ...
1
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1answer
57 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 ...
4
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1answer
60 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
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1answer
45 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
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2answers
81 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
102 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 ...
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0answers
53 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
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3answers
51 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
74 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
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2answers
45 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
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2answers
64 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 $$1 + 2 + 3 + \ldots + 2015 + 2016 + \ldots + 4030$$ ...
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1answer
28 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
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1answer
38 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 ...
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1answer
45 views

mathematics question [closed]

If 1 1 1 1 =R 2 2 2 2 =T 3 3 3 3 =E and 4 4 4 4 =N then 5 5 5 5 =?
1
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1answer
245 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
53 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 ...
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2answers
40 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
62 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?
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1answer
45 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?
5
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0answers
77 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
86 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 ...
7
votes
0answers
146 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 ...
80
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
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1answer
21 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
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1answer
53 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
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2answers
86 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 ...
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1answer
53 views

kind of mathematical puzzle

i was recently doing this problem--- problem statement You have r red, g green and b blue balloons. To decorate a single table for the banquet you need exactly three balloons. Three balloons ...
3
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3answers
371 views

Math Puzzle: Largest number which cannot be written as the sum of distinct fourth powers

I've come across this question which I can't seem to solve. Write the largest number that cannot be written as the sum of distinct fourth powers. First I'm stuck with the interpretation: I was ...
2
votes
2answers
91 views

Enumeration of Solved Sudoku puzzles

I tried asking this on StackOverflow and it was quickly closed for being too broad, so I come here to get the mathematical part nailed down, and then I can do the rest with no help, most likely. From ...