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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.

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-5
votes
1answer
54 views

Another how to kill 7 submarines

7 submarines are placed on an x, y grid - 0 to 111. They are located on whole numbered locations. Each submarine starts from any selected location with a given fixed speed and fixed direction, ...
5
votes
2answers
881 views

Euler's identity

Warning: this question requires knowledge of complex numbers. An Euler's identity is an identity, in which each of the following appears once and only once: the constant $0$: neutral element for ...
11
votes
5answers
2k views

A robot surviving on top of a 3x3 platform

A robot sits in the central square on top of a 3x3 platform. The robot can move up, down, left or right, but if it steps off the platform it will crash and die. You can preprogram the robot to make a ...
5
votes
1answer
754 views

Two super-button calculator

A calculator only has 2 buttons. The buttons are, however, very powerful: they are programmable buttons, i.e. you can pre-set them to be any function (meaning any map from $\mathbb{Z}$ to $\mathbb{Z}$)...
7
votes
3answers
168 views

Two button calculator

A calculator has only 2 buttons. The first multiplies the current value by 2, the second divides it by 3 without a remainder (so 8 becomes 2). Starting with 1 what is the least number of presses you ...
7
votes
3answers
1k views

Three button calculator part 2

A calculator only has 3 buttons. The first multiplies the current value by 3, the second adds 2 and the third subtracts 2. The calculator always starts with 0. What is the smallest positive even ...
10
votes
1answer
2k views

Three button calculator

A calculator has only 3 buttons. The first multiplies the current value by 3, the second adds 2 and the third subtracts 2. Starting with 0 what is the least number of presses you need to reach 100?
4
votes
1answer
213 views

Prime parallel rows for the first 20 numbers

Two positive integers can be joined with a straight segment if their sum is a prime and the segment doesn't intersect any other segments. What is the most number of pairs you can join if you can place ...
1
vote
1answer
140 views

How to kill 7 submarines

7 submarines are placed on an x, y grid - from negative infinity to positive infinity. They are located on whole numbered locations. Each submarine starts from a location with a given fixed speed and ...
2
votes
1answer
91 views

The first 10 prime butterflies

A prime butterfly is a set of three distinct numbers $a,b,c$, such that $a+b$ and $b+c$ are both primes. Can you divide numbers from 1 to 30 into 10 prime butterflies?
7
votes
2answers
158 views

Turning a fan on

I bought an air purifier which has [off, low, medium, high] settings and a single button. If it is on, the first button press activates the lights and subsequent presses increment the level with off ...
-5
votes
1answer
98 views

Find the next number in the weird sequence

The following sequence has been made using a specific pattern and the last number is kept secret. We have to find that number along with the pattern followed to make the sequence. 3, 11, 32, 71, ...
-2
votes
1answer
121 views

Missing Number Picture Puzzle

This is is logical reasoning puzzle in which your challenge is to find the relationship among the given numbers and then find the value of the missing number. Source: https://www.funwithpuzzles.com/...
5
votes
0answers
285 views
+50

Locked Door Number Puzzle

I'm supposed to make a delivery to a crazed botanist. In case you're curious, the shipping manifest is: ...
9
votes
3answers
557 views

Discover the six-character password!

You are given several pieces of paper which are as follows: (Unfortunately, a textual rendering is very difficult with this puzzle, so if someone can offer a suggestion on how to do it, that would be ...
2
votes
0answers
157 views

Code Breaking ( Sort of )

So someone sent me this code breaking/riddle to solve and I got really confused on it. I do need help on it, The Code needs to come out into a Phrase ( group of words ) CLUE 1: 2210232013400 - ...
1
vote
0answers
70 views
0
votes
0answers
124 views

3 bags of coins, find which bag contains fake coins, doing only 1 weighing

Probably a very easy puzzle for you guys; my point is more a mathematical one. FYI, it was shown in an episode of Columbo. You have 3 bags of coins. Each bag contains 50 identical coins. Two bags ...
10
votes
5answers
406 views

2 fake coins from a pile of 30 coins

You need to find two fake coins from a pile of 30 coins. You know that a fake coin has a different weight to a real coin, but you don't know whether it is lighter or heavier. You also know that all ...
8
votes
10answers
5k views

There are polygons with only right angles which have an odd number of corners

One of the interesting myths about a certain building in our university is that it has 13 corners. One way to dismiss this claim is to point out that a polygon with right angles must have an even ...
5
votes
2answers
267 views

Two equal-sized lists that produce prime sums

Place one or more distinct numbers between 1 and 100 into the lists $𝑃$ and $𝑄$, such that they contain the same number of elements and any number from $𝑃$ added to any number from $𝑄$ gives a ...
15
votes
5answers
919 views

Dividing the first 20 numbers into 3 lists

Place every number from 1 to 20 into one of three lists $P$, $Q$ or $O$, such that any number from $P$ added to any number from $Q$ gives a prime. What is the fewest number of elements that can be in $...
7
votes
4answers
527 views

How to make the number 49?

You've to start with $1$ and can use each of the following operations at most once. You can do the following in any order you like: 1) Add $2$. 2) Add $3$. 3) Add $5$. 4) Multiply $2.$ 5) ...
7
votes
1answer
280 views

Density type puzzle 5

A puzzle in the spirit of this puzzle. I've tried to make it a bit tougher this time, though there are no distractions of any kind. Enjoy! Final answer: (4,5) Hint 1 Hint 2 Hint 3 Hint 4
-2
votes
1answer
130 views

On which day the pond will fill half? [duplicate]

A pond has flowers in it each day the flowers in the pond get doubled if the pond gets full-on 20th day, on which day the pond will fill half? How? We are sitting here in the office in a group and ...
7
votes
2answers
697 views

Paint numbers from 1 to 23 with three colours

Can you paint every number from 1 to 23 with three colours, such that there are no distinct numbers $𝑎,𝑏,𝑐$ of the same colour with $𝑎+𝑏=𝑐$? For example, you cannot have 2, 3 and 5 of the same ...
5
votes
1answer
404 views

Paint numbers from 1 to 8 with two colours

Can you paint every number from 1 to 8 with two colours, such that there are no distinct numbers $a, b, c$ of the same colour with $a+b=c$? For example, you cannot have 2, 3 and 5 of the same colour ...
7
votes
1answer
202 views

Identify the odd one out element

There are two columns (two sets), in each set there is a pattern among the 7 elements. The elements are not arranged in any order, the two patterns are not necessarily the same, but they are related ...
1
vote
1answer
99 views

Last Person Remaining Avoids Death [duplicate]

There are 1600 people sitting around a circular table. The first person (person 1) has a sword and kills the second person then hands it to the next alive person (in this case person 3). Person 3 ...
6
votes
3answers
637 views

Number Equation Matrix

Can somebody please solve this? My daughter's school teacher gave her this puzzle to solve at home. But to me it seems a little out of order, and that's why I am asking here for help.
4
votes
2answers
164 views

Covering an 8x8 grid with W pentominoes

What is the minimum number of W pentominoes you need to cover every cell of an 8x8 grid? Pentominoes may overlap each other and sit outside the boundary of the grid. They can also be rotated in any ...
14
votes
6answers
2k views

Covering an 8x8 grid with X pentominoes

What is the minimum number of X pentominoes you need to cover every cell of an 8x8 grid? Pentominoes may overlap each other and sit outside the boundary of the grid. An X pentomino looks like this:
0
votes
4answers
123 views

Rectangles formed from every tetromino, tromino and domino

Can you form a 4x7 rectangle from every tetromino, tromino and domino? There are 5 different tetrominoes, 2 trominoes and 1 domino. Can you find different arrangements that are not mirrors/rotations ...
16
votes
1answer
1k views

Find d this ones stumped me help?

This one is annoying me so much. Got this from a maths teacher.
0
votes
1answer
186 views

A town E miles away?

I got this from my maths teacher What is the value of 'E'?
6
votes
2answers
475 views

10x10 grid with no unpainted hexominoes

What is the smallest number of cells you need to paint in an 10x10 grid, such that it contains no unpainted hexominoes? Note that a hexomino is a set of 6 adjacent cells (horizontally or vertically). ...
4
votes
2answers
364 views

8x8 grid with no unpainted pentominoes

What is the smallest number of cells you need to paint in an 8x8 grid, such that it contains no unpainted pentominoes? Can you find multiple solutions? Note that a pentomino is a set of 5 adjacent ...
3
votes
2answers
184 views

10x10 divided into the most number of rectangles of different area

How can a 10x10 be divided into rectangles such that there are as many as possible and they all have different area? Can you find multiple solutions that are not mirror/rotation of each other? Good ...
0
votes
1answer
51 views

7x13 rectangle divided into 13 different rectangles

Can you divide a 7x13 rectangle into 13 rectangles all of different area? Can you find multiple solutions? Note that rotations and mirrors don't count as separate solutions. Here is a similar puzzle ...
0
votes
3answers
76 views

4x7 rectangle divided into 7 different rectangles

Can you divide a 4x7 rectangle into 7 rectangles all of different area? Can you find multiple solutions? Good luck! P.S. @Deusovi wanted me to make puzzles that have an "aha moment", so here is my ...
4
votes
1answer
146 views

Prime magic star

Can you replace the letters with 10 consecutive primes such that the sum of numbers on each line is equal? I expect this to be solved with a computer. Good luck!
3
votes
1answer
147 views

Partition a 3x3 square into rectangles [closed]

Yesterday I watched "The man who knew infinity" about the amazing Ramanujan. Inspired by the partitions problem from the movie I came up with a puzzle: In how many ways can you partition a 3x3 grid ...
5
votes
3answers
201 views

Rawrdon Mamsay pays a visit

Now, I should warn you, this is one of my practical problems; meaning I don't know the solution and the answer's probably anticlimactic (like this or that). Still... My old pal Rawrdon Mamsay is soon ...
-4
votes
0answers
70 views

Find numbers 30-50 using numbers 2,0,1,9 only, with PREMDAS [duplicate]

You can only use numbers 2, 0, 1, 9, but they do not need to be in order. You can only use the numbers once unless they are used again as an exponent. You can only use subtraction, addition, ...
8
votes
1answer
640 views

A curious 5x5 square

Can you fill a 5x5 grid with numbers from 1 to 5, such that every number occurs exactly once in each row, exactly once in each column and exactly once in each broken diagonal (in both directions)? ...
0
votes
2answers
95 views

Painting edges of a 3x3 grid with 4 colours

Can you paint the edges of a 3x3 grid with 4 colours, such that: The colours of edges of every 1x1 square are different. The colours of edges adjacent to every vertex are different. Here is a ...
0
votes
1answer
61 views

Painting edges of a 2x2 grid with 4 colours

Can you paint the edges of a 2x2 grid with 4 colours, such that: The colours of edges of every 1x1 square are different. The colours of edges adjacent to every vertex are different. Good luck!
8
votes
0answers
131 views

The Flippin' Magician's 7-card Grand Finale

This question is a followup to this question by @ais523, which itself was a followup to this question by @Wen1now. After touring the globe to accolades when performing his 10-card trick and 8-card ...
3
votes
2answers
182 views

Cross the pond, but there's a catch!

There is a square pond, conveniently divided into segments, with coordinate $(0,0)$ in the bottom left and $(10,10)$ is the top right. You have planks length $2$ and $3$. You start at $(0,0)$ and ...
15
votes
3answers
998 views

Transferring 9 pegs on a 9x9 grid

You are given a 9x9 grid with a set of 9 pegs (red circles) arranged in a 3x3 pattern in the corner, as shown below: A peg can jump over another adjacent peg in any direction (horizontal, vertical or ...