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Questions tagged [mathematics]

A puzzle strongly related to mathematical facts and objects, or whose solution needs serious mathematical arguments. General mathematics questions are off-topic but can be asked on Mathematics Stack Exchange.

6
votes
5answers
367 views

Soar High for You? No Way!

Me and my fellows upon a time, Have earned the championship in our prime. Alas! That time has passed, my dearest fren', But we are still often used, according to Ben. Soar high for ...
9
votes
2answers
567 views

A differential equation with a hidden sentence

Find the specialized solution of $H''(r)-aH'(r)=0$ that satisfies $H'(0) = \frac{1}{p^2}$ and $H(0) = \frac{H'(0)}{a}(1+\frac{N}{Y}e^w)$ The question: Solve the above mathematic question Rewrite ...
2
votes
0answers
92 views

Write $\sqrt{5}$ as sums of powers of $1 + \sqrt{2}$? [closed]

The number $A = 1 + \sqrt{2}$ solve the equation $A^2 = 1 + 2 \sqrt{2} + 2 = 1+2A$. We also have that $$0 < \dots < A^{-2} < A^{-1} < 1 < A < A^2 < \dots $$ The powers are in ...
13
votes
3answers
659 views

Simple Maths Riddle 5

Here's a special one for you! I am prime, I am composite Sum my digits and half; I'll be perfect! Don't multiply them, I won't yield a thing But don't worry, it's only the beginning! ...
16
votes
1answer
492 views

To solve a simple heist

It happened by chance really. I was walking out from the bank when a man ran into me while rushing out. During our collision a piece of paper fell from his pocket. I quickly picked it up and tried ...
18
votes
2answers
2k views

A strange computer programming language

Here is a list of rational numbers: $\frac{22}{21}, \frac{7}{11}, \frac{13}{7}, \frac{51}{65}, \frac{13}{17}, \frac{1}{13}, \frac{15}{2}, \frac{7}{1}$ This list is actually a computer program! It ...
3
votes
3answers
1k views

Three coins for the fair king [duplicate]

Based on the question Eight coins for the fair king: I saw a comment saying "There isn't a good solution known even with three coins in all cases". So the challenge here is to try to solve the same ...
3
votes
1answer
131 views

Another variation of the game of Nim

Two players set several piles of chips. The piles are arranged in a row from left to right. By turns each player takes one chip from one of the piles and adds at will as many chips as he/she wishes (...
12
votes
4answers
603 views

A Chwistmas Widdle With a Twist

Chwistmas is the same with or without me, though I do wish you all Mewwy Chwistmas... I wish to be wid of my condition I am named and famed with humiliation A small happy square wheel! ...
3
votes
4answers
419 views

What will be the next term in this mathematical sequence?

What will be next in this series? $$0, 6, 24, 60, 120, 210, ...$$ I've tried it and noticed that the numbers are multiples of six. But I couldn't make a relation between them.
15
votes
2answers
410 views

What is the optimal strategy for this triangular board game?

I saw a board game somewhere and I want to know the optimal strategy for it. The game is played on a triangular board with 21 slots: The two players, red and blue, take turns to put numbered circles ...
2
votes
1answer
203 views

Help solving a math puzzle table

I am struggling to find the answer. Here is the source: math logic puzzle phone app.
45
votes
6answers
3k views

Eight coins for the fair king

You are responsible for creating new types of coins for the court. King respects the forgetful: he wants you to create 8 coins of different value, no more. King respects the feeble: he wants that any ...
2
votes
1answer
120 views

Just a little sum-thing

Select 5 numbers. Using exactly five copies of each, simultaneously create 15 (multi-)sets, one of each sum from 1 to 15 inclusive. Thanks to Gordon Hamilton for the inspiration...
0
votes
1answer
102 views

Who wins the game?

Two people play a game. The first one (A) picks one number from 1 to 10 and then the second one (B) also picks a number from 1 to 10 and adds it to the first number; the next round continues in the ...
0
votes
4answers
189 views

What is the missing number in the picture

interesting puzzle from facebook
6
votes
3answers
484 views

My Grandpa's Box #1

My grandpa died last month. At the reading of his will, he left me a strange wooden box. A post-it-note on the side read "You were always good at puzzles." There was a number lock on the front that ...
0
votes
2answers
113 views

Use all 10 digits to find the answer [closed]

Use all 10 digits to find the answer (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) _ _ _+ _ _ _= _ _ _ _
10
votes
1answer
2k views

Lost first game – can I still make my mother proud?

I am one of the greatest finger wrestlers of my generation. Only 0.1% of all players are better. When I play against someone who's worse than me, I win 99% of the time. Against someone who's ...
7
votes
1answer
491 views

What is the Unit Digit of the Sum?

I am thinking of 2 integers $x$ and $y$ which follow the following; $$2≤x≤y$$ $$x+y≤47$$ I then write the sum $S = x+y$ and the product $P=xy$ on two separate cards. I pass the sum card to player A ...
4
votes
3answers
369 views

Who is John's favourite painter?

John being his usual self forgot the name of his favourite painter. He went to the Oracle for assistance but inadvertently walked in on her while she was busy eating pie. Angry at the interruption, ...
4
votes
8answers
524 views

Finni's tricky game

Finni’s game: Person A thinks of a number (1 to 10). This number is called n. Person B says a number (1 to 10). This number is called x. Person A tells the absolute difference of n and x. This ...
4
votes
2answers
202 views

5 Digit Code Puzzle

We have a 5 digit code, any place can take 1 2 or 3. How do I find where the 2 is placed (if placed) knowing this criteria? 1) If the 1st digit is not a 3 then the 2nd is. 2) If the 1st ...
3
votes
1answer
111 views

How many possibilities are there for the buried treasure?

You have discovered a map to some buried treasure on an island the shape of a circle. The map has 9 markers which represent posts situated on the edges of the island. The 9 posts are located; North, ...
3
votes
2answers
115 views

Simple and intriguing

Five friends are sharing information about the marbles they have attempting to derive the total amount of marbles they own without disclosing to others the amount each own. They decide to do it by ...
2
votes
1answer
90 views

14sums - the diamond standard

My initial question had lots of answers, and my second had too many constraints. So, I have removed some constraints and added another. Same rules as before, but we are now using $[0,6]\cap\mathbb{Z}$....
1
vote
1answer
351 views

Will two kangaroos ever meet after making same number of jumps?

There are two kangaroos on an x-axis ready to jump in the positive direction (i.e, toward positive infinity). The first kangaroo starts at location $x_1$ and moves at a rate of $v_1$ meters per jump. ...
4
votes
2answers
141 views

Probability in Fighting Tournament in which Contestants consume each other

A tournament has 2 teams of 24 people each of weight 1. Each team sends one person into the pit where they fight until one consumes the other taking on all their weight. The probability that one ...
5
votes
1answer
128 views

21sums - more constraints

My initial question had lots of answers, as we can practically choose the middle square to be anything we want, and work outwards to the exterior edges, with the corners providing the flexibility ...
5
votes
7answers
1k views

9sums - a logical deduction puzzle

Each set of minuses contains an integer in the range [1,5]. The given numbers are the sum of the surrounding 4 numbers. --- --- --- --- 13 14 11 --- --- --- --- 11 ...
6
votes
3answers
215 views

Finding both fake coins in a set of $5$

There are $5$ rupees on Arnav's table. He knows that exactly $2$ of the rupees are counterfeit. One of these $2$ coins is lighter than a normal (non-counterfeit) rupee, and one of these $2$ coins is ...
2
votes
3answers
228 views

Infinitely many stacks of infinitely many cards on infinitely many tables

You are trapped in a room. In front of you, there is a table on which there is an infinite number of stacks of cards each containing an infinite number of black or white cards. Two stacks are ...
7
votes
5answers
425 views

Cutting a Slice of Cake Into Two

Driven out of a serious question, when sharing a slice of cake in a coffee shop how can my two friends split it without going down the middle (the cake is likely to crumble if you do this!) Given a ...
5
votes
1answer
104 views

Shortest path for delivering packages [duplicate]

A version of the Travelling Salesman Problem, but with certain points. We are talking about a town where 8 canals run from the middle boathouse into the city. You can only travel one way on the green ...
0
votes
1answer
73 views

What is the area of the shaded region? (Overlapping areas) [closed]

What is the area of the region poly1 formed by the arcs 'cdke'. The square is of sides 10 units long. The region poly1 is formed by four overlapping quadrants.
7
votes
3answers
536 views

Three Visual Puzzles

I'm designing a puzzle game, and am trying to play-test some concepts. Can you solve these? 108153767833 = A + B + C. What are the components and why? Note for C: As a hint to correct an oversight, ...
4
votes
2answers
177 views

The bottle(s) of pills of a different weight

I am a laboratory man dealing with random medicine. Day 1 I have 10 bottles of pills. 9 of them contain good pills that weigh 1.000g each, and the other one contains bad pills that weigh 0.999g each....
7
votes
3answers
777 views

Gaby and Jack's Number Guessing Game

Gaby, a good mathematician, thinks of a whole number between 1 and 100 inclusive. What is the least number of questions Jack needs to ask her, and what questions should those be, if he is to work out ...
1
vote
2answers
358 views

What is the next number in the given series?

I know that next number questions are not popular here, but this one is tough and I couldn't figure out the pattern. To give an idea one of the questions had a pattern of Prime(Fib(n)). So this is ...
3
votes
1answer
150 views

Three-digit multiplication puzzle, part III: Return of the Hex

Followup to: Three-digit multiplication puzzle and Three-digit multiplication puzzle, part II: ever heard of senary? Place different three-digit hexadecimal numbers (000-FFF) on each of the seven ...
-3
votes
2answers
274 views

Brain Testing Logical Reasoning Puzzle

Can you answer this logical puzzle? Puzzle Source: https://www.funwithpuzzles.com/2018/12/brain-testing-logical-reasoning-puzzle.html
3
votes
2answers
140 views

Three-digit multiplication puzzle, part II: ever heard of senary?

Followup to: Three-digit multiplication puzzle I'd never heard of "senary" either, until creating this series of three puzzles. It seems that "senary" is the word for base-six notation. Who knew? ...
16
votes
2answers
2k views

Blind Person Ball Game

You are blind and your friend presents you with 6 equal balls of which 3 are red and 3 are green. You friend challenges you to game to find a green ball. You must select 3 of the balls and your friend ...
4
votes
1answer
183 views

Three-digit multiplication puzzle

Place different three-digit numbers (000-999) on each of the seven nodes of the following diagram: There are six lines in the diagram, on each of which are three of the nodes. On each of those lines, ...
4
votes
1answer
211 views

The Housing Estate

A constructor wishes to build a housing estate in a square terrain with 64 (8 x 8) smaller plots of land, at most one house to a plot. Local urban rules allow building a house in a plot only if at ...
-1
votes
3answers
128 views

Which number is missing from the bottom grid? [closed]

It's a hard puzzle, can you find the missing number?
-5
votes
2answers
75 views

MATH PUZZLE ABOUT SEQUENCE [closed]

In the array of numbers below, each number above the bottom row is equal to three times the number immediately below it. What is the value of x+y? ...
7
votes
1answer
491 views

Fourteen numbers around a circle

Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
12
votes
3answers
770 views

The Mxied Atdiiodn

It has been swohn that to raed a txet the oedrr in which the lrtetes of each idniaduvl word aepapr is not ipmotanrt, so lnog as the fsrit and lsat ltetres are the correct oens. This is not the case ...
7
votes
2answers
562 views

Primes and Squares

Place a different prime or square number on each of the fifteen disks below so that the number in any disk that lies on two others is the sum of the numbers in those disks. Do so in such a way that ...