Questions tagged [mathematics]
A puzzle related to mathematical facts and objects, whose solution needs mathematical arguments. General mathematics questions are off-topic but can be asked on Mathematics Stack Exchange.
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Unexpected answer to sequence riddle
I've got the following sequence:
11+11=4
12+12=6
13+13=8
14+14=?
I've tried multiple approaches:
Assuming that the formula is ...
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2
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12 piece cube packing puzzle
Consider the following hexacube (made from 6 unit cubes):
GOAL:
Pack a 3 x 3 x 3 cube using three of these hexacubes plus nine unit cubes.
This puzzle comes from: https://puzzlewillbeplayed.com/333/...
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25,42=90: find the math pattern
I've got the following pattern:
25,42=90
62,31=92
73,12=?
What rule should I apply to 73 and 12 in order to get the answer? With brute force, the answer is
but ...
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1
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Math puzzle: 8,5=100
I'm a bit stuck with this puzzle (image)
8,5=100
10,4=80
16,2=?
I've tried 40,52,62,68 but no luck.
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One more "What does this operator do" question
it is fun to observe that questions like this What does this mathematical operator do? raise more new questions than correct answers!
When trying to solve the original question, I came to this new ...
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Find the next digit in four given sequences
Find the next digit in each of these four sequences:
7 8 8 8 8 ...
3 4 5 2 5 ...
2 1 2 1 2 ...
1 1 9 6 3 ...
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Can you pack these pentacubes to form a rectangular block with at least one odd side length other the side whose length must be a multiple of 5
This puzzle is part of the Monthly Topic Challenge #11: Now in 3D.
Consider the following pentacube (made from 5 unit cubes):
It is possible to pack four of these pentacubes to form a 2x2x5 ...
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1
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Chem-is-try is hard
You are a chemist and ask your coworker to puzzle you. They give you this puzzle and ask you to solve it.
LiPSiNArHCaScMgHCaFPSiK
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2
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Old School Measuring
You have an obscure job in 1600's Brussels. You make reference sticks. You own a high-quality ruler (which are quite rare in that era) and use it to cut lengths of wood or metal to certain lengths ...
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Median is the mean
Can you divide the numbers 1 to 10 (inclusive) into two sets of 5 numbers each, such that the median of the first set is the mean of the second set, while the mean of the first set is the median of ...
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Combine 1,3,3,7 to get 10
I tried lots of combinations but could not find a solution. Each number has to be used exactly once, the allowed mathematical operators are
Addition: +
Subtraction: -
Negation: (unary prefix) -
...
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1
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2023 From Numbers 1-15
Using the numbers 1, 2, 3,..., 15, in that order, how can you make the number 2023 using the +, -, $\times$, and $\div$ operations. (You can use as many parentheses as you want.)
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2023 Squared From Squares
Without moving or removing any number, replace each of the triangles by either $+$, $-$, $\div$ or $\times$, and insert as many sets of parentheses as you want, in order to make the following equality ...
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What does this mathematical operator do?
The solution to this puzzle is one I came up with when working on this puzzle: What is the answer of this math puzzle?
For two natural numbers a,b, can you figure ...
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Just one symbol that answered a question
I was doubting whether or not to go on vacation. So I asked someone if I should go.
The answer was given on a piece of paper, with only the following symbol:
∟
What did it mean?
Added hint:
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What is the answer of this math puzzle?
One of my friend brought this simple-looking math puzzle to me, but it was harder than it seems.
I tried several ideas including simple arithmetic operations, and even considering base-n.
...
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Find the right key as fast as possible
I have a number of keys on my keyring and want to find the correct key as fast as possible.
Unfortunately, all the keys look the same. However, I can see if the teeth are turned the same or opposite ...
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2
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Replacing Untold Billions
First:
Assume Earth's population is 8,037,860,611 and they have ID numbers 1 through 8,037,860,611
You make a set of cards numbered 1 through 8,037,860,611
A robot goes to each person in turn and ...
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The Angel Problem - Sticker Devil Variation
So If you are aware of the angel problem, I propose a Variant:
we introduce the Sticker Devil: A normal devil, with the added ability to sacrifice his turn to color any and all White Tiles that are ...
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3
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Measure the rod
You are given three meter scales A, B, and C are shown in picture given below. The scales are however, quite unique in their properties as they have different numbers of division per meter. You are ...
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The magic number 376
376 is a magic number! When we raise it to some integer power then the result always ends in 376:
$376^2 = 141376$
$376^3 = 53157376$
$376^4 = 19987173376$
$376^5 = 7515177189376$
$376^6 = ...
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votes
1
answer
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Intransitive urns
N balls with numbers 1,2,3...N are filled arbitrarily into 3 urns A,B and C - but no urn may remain empty. We write P(A,B) for the probability that a ball chosen randomly from urn A shows a higher ...
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Think in a Odd way
You have been captured for the crime of making a rude comment on Puzzling Stack Exchange and sent to Puzzlcatraz, a special prison for perfectly logical logicians. The warden is fair and decides to ...
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Making fair dice
Dmitry Kamenetsky asked the following two questions:
Making two fair dice
Making three fair dice
My question is a generalization of Dmitry‘s questions.
You are given N unlabelled standard 6-sided dice....
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votes
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Dissections of the "hat" aperiodic monotile
We all know the "hat" monotile by now, right? It can obviously be dissected into 8 congruent kites, or 4 congruent pentagons. Can it be dissected at all into 2 congruent shapes? What about 3?...
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Odd solutions are in 3d
This puzzle is part of the Monthly Topic Challenge #11: Now in 3D.
You are given a collection of sticks which are straight lines of length 1. Two such sticks can be attached to each other at their end ...
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votes
1
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A and B don't know their own values
() isn't used mathematically in this puzzle. () means that whatever is inside should be evaluated in the most suitable and ...
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2
answers
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Making three fair dice
You are given three unlabelled standard 6-sided dice. Can you write every number from 1 to 18 on the dice, such that in any given throw each die has the same chance of being the highest?
Here is a ...
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Making two fair dice
You are given two unlabelled standard 6-sided dice. Can you write every number from 1 to 12 on the dice, such that in any given throw there is a 50% chance of the first die being smaller than the ...
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Three clocks problem
Three clocks which show the times for three different time zones are hanging on a wall. The length of their minute hands is the same - but not the lengths of their hour hands. The lengths of the hour ...
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An Almost-squarish set of numbers
A set of numbers is called Almost-squarish if it satisfies the following two properties:
The set contains only positive integers.
The product of any two distinct numbers in the set is one less than a ...
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2
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Pick the odd one out: 214, 350, 520, 738
I am preparing for an exam(NTSE), and I came across this puzzle(aptitude) in one of the quizzes. book(study guide NTSE). The book's author is Arihant Experts.
The question is to Pick the 'odd one out' ...
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Pick the odd one out: 146, 821, 704, 603 [closed]
I am preparing for an exam, and I came across this puzzle(aptitude) question.
The question is to Pick the 'odd one out' and there are four options given.
146, 821, 704, 603
The correct answer is 603....
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1
answer
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Self-numbers and repunits
Self-numbers or Colombian numbers (A003052 in the OEIS) are natural numbers which are not the sum of a smaller number and the sum of its digits. Repunits (in base 10) are numbers consisting only of 1'...
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Three boats problem
Three boats are sailing on the ocean. The three boats form the corners of an equilateral triangle. Boat 1 heads southwards with a constant speed of 10 kn, boat 2 heads westwards with unknown constant ...
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Is there an answer to this 'turning my fan off' puzzle?
I have a ceiling fan with 4 states. The states always go in the order of off, high, medium, low, off. A cord pull will change the state.
One pull of a cord to turn the fan to the off state from the ...
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An animal climbing something (forward/backward slide): is there a generalized solution?
A snail is at the bottom of a 30 foot well. Every hour the snail is
able to climb up 3 feet, then immediately slide back down 2 feet. How
many hours does it take for the snail to get out of the well?
...
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Can you pack these tetracubes to form a rectangular block with at least one odd side length?
Consider the following tetracube (made from 4 unit cubes):
It is easy to pack two of these tetracubes to form a 2x2x2 rectangular block. And from that simple packing it is easy to pack any ...
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How many students in this Math circle and can they together explain the solution of all of the 20 problems?
A Math circle leader assigned 20 problems as homework. At the next meeting, he found out that each student solved exactly 2 problems, and that each problem was solved by exactly 2 students.
A) How ...
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1
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How to make 93 using only 2 0 2 4
How to make 93 using only 2 0 2 4? The digits can be used only once.
You can use
$+,-,*,/,Sqrt,X^y,!,!!,nCr,nPr$
You can also group 2 and 2 to make ‘22’ and you can also use the above method to make ...
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1
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Measuring distance with steps
I am trying to measure 100m for a children's foot race, but I forgot to bring my measuring wheel. I know that each of my steps is between 0.9m and 1.1m (sampled at uniform). I can only take full steps ...
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Continue the row of numbers: 1, 3, 9, 13, 65, ...?
Yesterday, I stumbled across a series of numbers that I could not solve. Maybe one of you can figure it out?
1, 3, 9, 13, 65, …?
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Green Triangles Puzzle
This question is closely related to Green Hexagons Puzzle.
Start by choosing some triangles to be green. If a triangle is sharing an edge with at least 2 green triangles, it becomes green. This ...
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Green Hexagons Puzzle
Start by choosing some hexagons to be green. If a hexagon is touching at least 3 green hexagons, it becomes green. This repeats for as long as possible. What's the minimal number of initial green ...
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Counting combinations with two dice
You are given two identical standard dice as shown below. You can stack them one on top of the other, or place them touching side by side. In all cases the face of one die must fully touch the face of ...
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Open the Door and Sleep Forever
Clues:
_ _ _ [plank of wood]
_ _ _ [musical note]
_ _ _ [rock]
34575 92200 172875 149825 172875 138300 242025 161350 80675 149825[line]11525
Instructions: Name That Landmark
_ _ _ _ T _ _ _ ...
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The secretary problem goes on budget
Secretary problem describes a scenario where a company wants to hire the best secretary from sequential interviews of candidates that can be done only once.
In budget secretary problem a company has ...
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Making perpetual motion machine from candy-sharing cats
It is well known that cats can be turned into perpetual motion machines under the right circumstances. Candy-sharing cats are such wonderful creatures that come in infinite supplies, called #1,#2,#3,.....
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How will the wolf catch the sheep in minimum time?
A wolf is trying to catch two sheep. At time $0$ the wolf's at $(0,0)$ and the sheep are at $(1,0)$. All animals move continuously in real time and react instantaneously according to each other's ...
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Do puzzles like "write 120 using four 8" have a specific name?
Here on puzzling SE there is the category "calculation puzzle", but it's very broad. I'd like to know if somebody gave a specific name for such puzzles.
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