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Mathematics Stack Exchange

Questions tagged [puzzle]

For questions about the mathematical principles behind puzzle, games, riddles, or their possible solutions. Questions that are not strictly mathematical in nature should be asked on Puzzling Stack Exchange.

Many puzzles, games, and riddles are based on mathematical concepts. This tag is for questions that ask about the mathematics behind a puzzle, game, or riddle, or about the solutions to mathematical puzzles.

If you already know the answer to the puzzle you are posting, you might consider posting your question on Puzzling Stack Exchange, instead. If you do end up posting your question on Mathematics Stack Exchange (MSE), please read the following meta posts on these kinds of questions before asking your question:

If you do end up posting on MSE, please make it clear in your question that you are "puzzling" the community and that you will be answer the question yourself if no one in the community posts your desired solution.

3301 questions
8
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How many days are needed to find the robot?

There is a row of $n$ opaque boxes numbered from $1$ to $n$. A robot is programmed with an ordered pair of numbers $(x,y)$, each being integers between $1$ and $n$, inclusive. $x$ is the box the robot will be in on the first day, and $y$ is the…
DreiCleaner
  • 1,497
8
votes
3 answers

Does Ball Sort Puzzle always have a solution?

In this game we have $4$ balls of each colour and $n$ different colours, for a total of $4\times n$ balls, arranged in $n$ stacks. In addition, we have $2$ empty stacks. A maximum of $4$ balls can be in a any stack at a given time. The goal of the…
Patricio
  • 1,604
8
votes
5 answers

Father and daughter river crossing puzzle.

There are 3 men and 3 girls. lets name them ABC, A's daughter X, B's Daughter Y, C's daughter Z. Rule to cross the river: At once Only two Can go on boat. Only Men know how to drive the boat (So there has to be atleast one man on boat) No girl…
Rookie Programmer Aravind
  • 227
8
votes
8 answers

a finite sets problem

I was given the next riddle in one of the lectures: A jet plane with m ( a natural number) seats which is filled up to the maximum is about to take off. each passenger holds a card with a natural number in his hand which he cannot see nor can he…
Lola
  • 623
7
votes
6 answers

concerning a cheque

A man went into a bank to cash a check. In handling over the money the cashier, by mistake, gave him dollars for cents and cents for dollars. He pocketed the money without examining it and on the way home he spent a nickel. Later on examining it, he…
Four Seasons
  • 864
7
votes
5 answers

Bringing the fox, the goose and the cereal across the river unharmed

Solve puzzle algebraically? I can't come up elegant and algebraical solution. There are man, fox, goose, and cereals. If the man is not beside the fox, the fox will eat the goose. If the man is not beside the goose, the goose will eat the cereal.…
Taeyun
  • 109
7
votes
10 answers

A loss and gain problem

This is a very simple but confusing puzzle. A customer buys goods worth $200$ rupees from a shop. The shopkeeper selling these goods makes zero profit from this purchase. The lady gives him a $1000$ rupee note. The shopkeeper has no change, so he…
constantlearner
  • 203
7
votes
2 answers

Variant of the hardest logic puzzle ever

This question was reposted on puzzling.stackexchange and hexomino's answer there might be the correct one( although I am still not completely convinced). The following is the link to the reposted…
Hemant Agarwal
  • 211
7
votes
1 answer

Unfaithful husbands

In a parallel universe when Neil Armstrong landed on the moon, he found it to be inhabited by a tribe of humanoids. He discovered that: they were all married the husbands of 10 of the wives were unfaithful Each wife knew whether or not any…
Alan
  • 111
7
votes
1 answer

A Nim game variant

We know how to win the classic regular Nim (two players) Classic rules: Any number of beans into any number of separate piles Each move, the player whose turn it is, must choose one pile of beans and remove anywhere from one bean to all the beans in…
Jean-Pierre
  • 1,043
7
votes
2 answers

Find missing number from sum of first few natural numbers

A child was asked to add the first few natural numbers $1+2+3+...$ as long as his patience permitted. As he stopped, he gave the sum as $575$. When the teacher declared the result wrong, the child discovered that he had missed a number in the…
Harish Raj
  • 267
7
votes
4 answers

A math teacher thought of a positive integer of two digits.

A math teacher thought of a positive integer of two digits. She wants her two intelligent students Hanna and Charlie determine the exact number thought. For this, Hanna is privately told how many positive divisors the number has; Charlie, the sum of…
Henfe
  • 1,208
7
votes
1 answer

Maths question from an IQ test

It is possible that 25 is the correct answer since I guessed (educated guess) that and got a predication of 170 IQ (obviously not accurate) I saw that 63 + 25 = 88 and 16 + 9 = 25 but then that breaks apart the lower you go. Any ideas? I saw that…
Ghozt12
  • 99
6
votes
4 answers

Puzzle: numerical pattern recognition

IF 7 - 3 = 10124 6 + 3 = 3279 5 – 2 = 763 11 + 2 = 92613 Then, 15 - 3 =? Any ideas ? I dont know how I am supposed to go about solving puzzles like this one ? is there any strategy ? any algorithm ?
Chani
  • 7,871
6
votes
1 answer

The Fox And The Duck Puzzle

A duck, pursued by a fox, escapes to the center of a perfectly circular pond. The fox cannot swim, and the duck cannot take flight from the water. The fox is four times faster than the duck. Assuming the fox and duck pursue optimum strategies, is it…
Srikanth Nakka
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