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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2
votes
2answers
106 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 ...
0
votes
1answer
464 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
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 ...
0
votes
3answers
33 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 ...
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 ...
0
votes
1answer
328 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 ...
-2
votes
3answers
940 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 ...
-6
votes
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 ...
-2
votes
0answers
30 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
58 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 ...
1
vote
1answer
488 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
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 ...
17
votes
8answers
2k views

The Three Princesses

Is it possible to solve this problem: A prince wish to marry a princess. There are 3 princesses, one is young, one is a little older and one is old. The prince is able to tell the princesses apart. ...
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 ...
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 ...
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
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 ...
-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 \\ ...
2
votes
1answer
68 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
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 ...
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 ...
-5
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
130 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 ...
2
votes
2answers
99 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
59 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 ...
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 ...
2
votes
2answers
335 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
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 ...
1
vote
5answers
233 views

Apple puzzle math

A salesman had 25kg apple. For convenience, he put some apples in 3 types of boxes, boxes of 1kg, 3kg and 5kg. He has a total of 10 cases of various kinds. Can he put 25kg apple to fit into 10 ...
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 ...
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. ...
4
votes
3answers
6k views

Probabalistic proof of green-eyed dragons logic puzzle

I came across the "green-eyed dragons" puzzle (alternatively known as the "blue eyed villagers" puzzle). The typical proof uses a straightforward inductive strategy. I came up with a probabalistic ...
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
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... ...
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 ...
0
votes
1answer
84 views

How can you make every student happy?

This is a problem my friends and I are trying to solve. As respect to their privacy, I'll use variables. There are three tables, each able to hold up to 8 students. Student A cannot sit with more ...
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 ...
2
votes
2answers
538 views

Seating Arrangement puzzle.

Not sure if its a correct place to post these kind of questions. Eight persons-P,S,Q,R,U,B,J and C are sitting in a field in a circle. Three are facing opposite side and other five are facing the ...
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 ...