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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5answers
4k views

Absolute values of 1-10 in a pyramid form

_ _ _ _ \/ \/ \/ _ _ _ \/ \/ _ _ \/ _ you have numbers 1-10. you can only use each number once and the number below is equal to the absolute ...
5
votes
3answers
109 views

100-Sided Dice “Blackjack” Game

I am attempting to determine two variables in this game: The optimum strategy: (What number the bettor should stay at) The expected value given perfect play: (The percent return on a bet when using ...
2
votes
1answer
57 views

Farthest Possible Distance for a Truck Fleet When Transferring Gas

Given a fleet of 50 trucks, each with a full fuel tank and a range of 100 miles, how far can you deliver a payload? You can transfer the payload from truck to truck, and you can transfer fuel ...
4
votes
3answers
96 views

Compass-and-Straightedge Construction [closed]

I stumbled upon this question in math class, and I got stuck. The Question: You're are given a circle, and two points. How do you construct a circle that goes through the two points and is tangent to ...
3
votes
2answers
225 views

Superqueens on a chessboard

The superqueen is a chess piece that can move not only like a queen, but also like a knight. What is the maximal number of superqueens on an $8 \times 8$ chessboard such that no one can capture any ...
2
votes
1answer
350 views

How many triangles in picture? Formula or algorithm for this?

How many triangles are in this picture? Is there any formula or computer software to calculate this? Also: I know programming so I can program something to solve this if someone can point out an ...
0
votes
0answers
52 views

Weighing Coins Puzzle

Consider the following question: Suppose you have 8 coins. 3 of them weigh x units, 3 y units, 1 ...
1
vote
2answers
47 views

Alternate plain English algorithm for Towers of Hanoi

There are four plain English algorithms for the Towers of Hanoi Puzzle available on Wikipedia, but when I was first solving the puzzle, I came up with an algorithm that is different from any of the ...
3
votes
3answers
115 views

Puzzle: leaning a ladder at $45^\circ$ to a wall using only yourself

This question was asked to my friend in an interview. You are provided a ladder and are led to a wall. The ladder must be kept against the wall making an angle of $45^\circ$ with the floor. You are ...
1
vote
1answer
138 views

How many 3 digit even numbers can be formed by using digits 1,2,3,4,5,6,7 ,if no digits are repeated

How many 3 digit even numbers can be formed by using digits 1,2,3,4,5,6,7 ,if no digits are repeated ATTEMPT There are three places to be filled in _ _ _ I wrote like this _ _ 2 _ _ 4 _ _ 6 Now ...
57
votes
14answers
4k views

What is $x^y$? How to understand it?

$x+y=z$ I have a pen. He has a pen. Total is two pen. This is plus. $x-y=z$ I had two pens. A pen was lost. So, I have a pen. Total remaining is one. This is minus. $x\cdot y=z$ I have two pens. ...
0
votes
1answer
18 views

Distance and speed question on minimum time

Suppose that there is a narrow bridge 4 metres wide that only 1 bus can pass on it. The bus is travelling at 10m/s and it is moving with constant speed. A man is 2m away from the bus and is crossing ...
24
votes
5answers
255k views

How many squares actually ARE in this picture? Is this a trick question with no right answer?

This is one of those popular pictures on sites like Facebook. I always see a huge variation of answers such as 8, 9, 16, 17, 24, 28, 30, 40, 41, 52 etc, yet I've never seen a definitive answer on any ...
2
votes
1answer
11k views

Puzzle - 123456789 = 100 with three operations?

Given the sequence 123456789: You can insert three operations ($+$,$-$,$\times$,$/$) into this sequence to make the equation = 100. My question is: is there a way to solve this without brute force? ...
2
votes
3answers
85 views

economist puzzle for

Mr. White and Mr. Black agreed on the plan to average the wealth by pairs of economic classes, but they differed on the order. Averaging means that the total wealth of the two classes is ...
2
votes
1answer
47 views

Find the correct betting combination

Case 1: If we bet \$1 on team #1 and it wins then we will get \$2 Case 2: If we bet \$1 on team #2 and it wins then we will get \$4 Case 3: If we bet \$1 on team #3 and it wins then we will get \$6 ...
1
vote
1answer
84 views

Move a polygon to a specified position using only allowed rotations, reflections, and dilations

There is a puzzle in Recreational Math in Khan Academy which is very difficult to solve. This puzzle involves using a restricted amount of transformations. The question does not appear to work in the ...
4
votes
6answers
3k views

Is there a faster way to count jigsaw puzzle pieces?

I have a number of old 1000-piece jigsaw puzzles I'd like to sell. I'd like to make sure they are complete first. Is there a faster way to determine whether there are exactly 1000 jigsaw pieces than ...
2
votes
0answers
65 views

Has this puzzle got a name? [closed]

I really like this puzzle: https://www.youtube.com/watch?v=ud_frfkt1t0 Does it have a name? Has it been studied before? The question: Let $A$ and $B$ be independent and identical continuous random ...
80
votes
5answers
4k views

What is the smallest number of $45^\circ-60^\circ-75^\circ$ triangles that a square can be divided into?

What is the smallest number of $45^\circ-60^\circ-75^\circ$ triangles that a square can be divided into? The image below is a flawed example, from http://www.mathpuzzle.com/flawed456075.gif ...
4
votes
4answers
1k views

A 3rd grade math problem: fill in blanks with numbers to obtain a valid equation

Even though this is a 3rd-grade math problem, people found it extremely hard. Any people have a solution, or algorithm is welcome. I'll try make a program base on the algorithm and see if it's ...
3
votes
4answers
222 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 ...
6
votes
2answers
294 views

How many archers do I need to deploy to destroy an Archer Tower?

I was playing Clash of Clans and came across this interesting problem. Consider the case when I'm attacking an enemy war base with an Archer. My archer can cause a damage of 12 hitpoint per second. ...
2
votes
0answers
89 views

Math puzzle I have been stuck on

Have had this math puzzle that I have been unable to solve for a while. Each leter is a number between 1-9. No letter uses the same number twice (aka if B is 3 D can't be 3 also). The ? mark ...
2
votes
1answer
80 views

Difficult sequence puzzle

What is the 25$^{th}$ term of this infinite sequence? $$1,1,1,1,1,691,2,3617,...$$ I have tried for an hour now and I can't find any meaningful relation between the terms.
3
votes
1answer
3k views

Number Of races needed? [duplicate]

25 horses, 5 race tracks; we need to choose the top 3 horses. What is the minimum number of races you need? I have thinking deeply and figure out this: First race all 25 horses in groups of 5 to ...
1
vote
2answers
78 views

Question involving area and perimeter of two parallelograms sharing a diagonal.

Given two parallelograms $P1$ and $P2$ sharing a diagonal, such that area of $P1$ is greater than area of $P2$, can we say that the perimeter of $P1$ is greater than the perimeter of $P2$ ? Actually ...
2
votes
2answers
375 views

Four men seated in a boat puzzle

I am looking for an elegant way to solve this rather simple logic puzzle using mathematical logic (statements, conjunctions, disjunctions, implications, tautologies, predicate logic and so on). I am ...
3
votes
2answers
40 views

Searching specific numbers based on clues

"Find x for 0≤x≤100,000." My clues are as following. I'm not sure whether there are multiple answers or that only one 'x' remains based on these clues: This number isn’t between 20,000 and 40,000 ...
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 ...
2
votes
2answers
133 views

The Efficiency of Random Parking Problem

A few days ago in my Calculus BC class we were given a page of 6 challenging end of the year problems. That was a refreshing change from the drudgery we usually do (WebAssign). One of them went like ...
1
vote
1answer
50 views

Recursive Hexagon Problem to find number of hexagons at each stage

The source of this problem is this SPOJ question. Let me simplify it: A valid beehive is recursively defined as follows: 1. A single regular hexagon is a valid beehive. 2. To all the external cells of ...
0
votes
0answers
72 views

Not so obvious probability puzzle.

You are given two boxes with a number inside each box. The two numbers are different but you have no idea what they are. You pick one box to open; read the number inside; and then guess if the number ...
36
votes
3answers
1k views

Tall fraction puzzle

I was given this problem 30 years ago by a coworker, posted it 15 years ago to rec.puzzles, and got a solution from Barry Wolk, but have never seen it again. Consider the series: $$1, ...
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
311 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 ...
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 ...
-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 ...
16
votes
0answers
262 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
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 ...
1
vote
0answers
231 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
68 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
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 ...
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 ...
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
851 views

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

?+?+?=30 Please slowe this question and reple answer
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 ...