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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0
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3answers
27 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
1answer
94 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
36 views

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

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
vote
1answer
51 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 ...
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0answers
50 views

Mathematical analogie, Find the number [on hold]

I have this problem: 2 72 7 4 38 20 40 X 60 I try in multiples ways And i cant solve the problem, Can anyone solve it? I need get X, With the left and right ...
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votes
0answers
29 views

How many gold coins were there originally? [on hold]

Three persons together own a pile of about 200 coins. They originally possess $\frac12$, $\frac13$, and $\frac16$ of the coins, respectively. Now each person is going to take out some coins from the ...
4
votes
1answer
43 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 ...
3
votes
0answers
57 views

8-puzzle maximum moves

I'm programming a solver for an $n \times n$ solver but one of the question is what's the worst case of moves. I know if it's an $3 \times 3$ puzzle it's 31 moves but how do they calculate it? This ...
0
votes
1answer
42 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 ...
-2
votes
3answers
926 views

The solution to this problem and its mathematical operations [duplicate]

This is a logic test that was part of the Singapore and Asian Schools Math Olympiad – a competition for teenagers. Albert and Bernard just became friends with Cheryl, and they want to know when her ...
0
votes
2answers
57 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
92 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 ...
-4
votes
0answers
15 views

Names-to-Numbers puzzle [closed]

Based on these codes, find what Katie's code is: $$\begin{align} \text{Carrie}&:\;030112 \\ \text{Landon}&:\;120701 \\ \text{Camly}&:\;030326 \\ \text{Ben}&:\;020425 \\ ...
1
vote
0answers
48 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
49 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
67 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
42 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
61 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
26 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
36 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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votes
1answer
41 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
vote
1answer
129 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
51 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
32 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
60 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
42 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
votes
0answers
74 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
85 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
130 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 ...
76
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
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
votes
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. ...
1
vote
2answers
78 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 ...
1
vote
1answer
51 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
votes
3answers
359 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
85 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 ...
1
vote
2answers
158 views

The Probability Riddle

While working on a mathematical model we have come across a problem that seems easy yet has a bunch of intelligent, mathematically trained people start doubting themselves :). Riddle us this... ...
4
votes
2answers
39 views

Rearranging a Staircase Grid into a Square

Is there any way to rearrange the above "staircase" grid into three pieces that can be rearranged into the 6x6 square grid below it? I have tried this problem for over six hours and have not arrived ...
16
votes
2answers
447 views

The Weaver Android app $\rightarrow$ cute combinatorics problem

There's an Android puzzle app called "The Weaver". My question is why every level seems to be solvable in far fewer moves than one might naively think. Here's a link for people who want to play along ...
2
votes
1answer
40 views

Strategy for 2-player game, drawing uniform variables and optionally redrawing

Player 1 and Player 2 secretly and separately draw uniform random variables in [0,1]. They may (secretly) elect to redraw once and replace their value. Highest value wins. What is the optimal ...
1
vote
1answer
48 views

Quiz: people and hats

I've created this quiz, but I'm not sure if the answer that I've found is correct or not. Three people meet at a pub, each of them has a blue or a red hat on his\her head. Nobody knows the colour of ...
1
vote
1answer
106 views

Two Buckets Water Puzzle

When reading up on graph theory, I came across this puzzle and on further investigation, learned that a general solution for this is similar to this problem. However, I haven't been able to ...
0
votes
1answer
69 views

Buffons needle crossing both lines?

Buffon's Needle Problem : Given a needle of length $l$ dropped on a plane ruled with parallel lines $t$ units apart, what is the probability that the needle will cross a line? I am working out ...
1
vote
1answer
53 views

Combinatorics question about alternately-coloured diagonal halves of sides of a cube

Diagonal halves of each side of a cube are painted in alternate colours. Let the vertex at which such a half forms a right angle be its base vertex. What is the minimum number and the maximum number ...
1
vote
0answers
48 views

How to solve a “logic grid/table puzzle” as well as a “logic game” from the LSAT

Dear fellow members of the prestigious brotherhood of philosophical and mathematical logicians, I am familiar with symbolic logic on a level such as is covered in Patrick Hurley's textbook A Concise ...
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votes
1answer
68 views

Puzzle: Players A,B,C,D are in a line

Players A,B,C,D stands in a line. Players A, D do not move. round 1: player B moves one distance closer to the midpoint of A,C round 2: player c moves one distance closer to the midpoint of B,D ...
3
votes
0answers
95 views

Worst case in decanting puzzles (pouring water from one jug to others).

A classic puzzle is to start with $3$ jugs of nonzero integer capacity ($A \ge B \ge C$) and have some water (integer) in each jug (the initial position). The goal is to get to some final (integer) ...
1
vote
1answer
33 views

A very simple math puzzle: An object O weights 1 N and the half of the weight of object O. What is the weight of object O?

So, today I came across a very simple (or so I though) math puzzle. If this is the wrong StackExchange please point me to the right place to ask. The puzzle goes as such: An object O weights 1 N ...
0
votes
0answers
16 views

How to approach more Puzzle-like problems (octagon, intersection points)

In physics I understand the situation and can derive formulas to describe it. But when it comes to more puzzle-like math problems like this: "All 20 diagonals are drawn in a regular octagon. At how ...
7
votes
2answers
192 views

reversing digits and squaring

If we reverse the digits of $12$ we will get $21$. $12^{2}=144$. If we reverse its digits we will get $441$ which is $21^{2}$. Here is the puzzle. How many such two digit numbers are there? Digits ...