# 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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### How many scouts are there?

At camp every tent is given a number. My twin lives at the reverse of my tent number. The difference between our tent numbers ends in two. What are the lowest possible numbers of our tents? A problem ...
517 views

### Circle inside circle

Here's a fun little math problem I made(by fun I mean no complicated methods needed at all.) You have a large circle with radius N with a cross in it to seperate the 4 quadrants(so that the figure ...
331 views

### Crossword, but math!

This kind of puzzle is from my mom's puzzle magazines. There it is called Figure Logic. It is essentially a crossword, but with math. In crosswords, all words must be real words. In Figure Logic, no ...
2k views

### Make 28 with the numbers 2020

Try to make 28 from the numbers 2020. Allowed operations: +, -, x, ÷, ! (factorial), exponentiation, square root, squaring, parentheses.
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### Random walking on a board

There’s a pawn starting in the center of this game board. At each move, it can advance randomly towards any of the adjacent squares sharing a common side with equal chance. What’s the probability of ...
848 views

### The Starks, Parks, Clarks and their kids

Inspired by Martin Gardner's puzzle from his book John,a new student at the Math Department of the College, was invited to a get-together at one of the Professor's house. Professor Stark welcomed ...
211 views

### The special machine

There is a machine, which when you put a number card which has written $x$ on it, it will output a number card with $$x^2+10x+20$$ on it. John has a number card on his hand, then repeated the ...
3k views

### Alice and Bob play a game

The rain was still falling and Alice and Bob were terribly bored of having to stay inside the caravan, so they decided to play a game. The game is that Alice chooses a number $x$ in the interval [1,n] ...
900 views

2k views

### Boys and girls in a circle

There are $28$ students in a class, and each of them are either boy or girl. They sit in a circle, and claim that “The two people next to me are of different gender than each other.” It's known that ...
101 views

### Calculation puzzle 006

Find the number which corresponds to the place indicated by the question mark. ...
120 views

### finding a number using clues [closed]

The digit on hundreds place of a three-digit number is 2, the digit on tens place is 3 less than the digit on ones place. 6 times the product of the three digits is 20 less than this number. What is ...
226 views

### Cannonballs packing

A pile of cannonballs stacked like a pyramid has a rectangular base. Each layer has a length and a width in terms of cannonballs that are each one less than those of the layer that is directly below. ...
306 views

### Scientifically Themed Rebus/Dingbat Puzzles - Part 2

below are more rebuses with "scientific" expressions that represent something in popular media. Part 1 here. One of the questions in Part 1 has a link to a question here.
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### Knights on a Torus

An 8×8 chessboard is in the shape of a torus. (This means that the board "wraps around" - you can go left from a2 and come out on h2, for instance. It also works vertically - you can go up from f8 and ...
821 views

### Scientifically Themed Rebus/Dingbat Puzzles

Below I have created a list of a few "scientific" expressions that represent some form of popular media, with the type stated. Hope you enjoy.
782 views

### Exam statistics

250 teenagers gather for an exam. Peeking at the roll, a math-inclined among them note that if they are split into 10 groups of 25 per alphabetical order, then in each group, there are two with the ...
259 views

### Find a good strategy to survive the multiplayer duel

Alice is involved in a duel with $N$ other opponents. She can choose a gun for herself with any hit probability as she wishes. She also prepares guns for her opponents, whose hit probabilities she can ...
175 views

### Calculation puzzle 005

396 ? 556 99 872 664 I tried to solve it but to no avail. Possible answers are 666, 491, 654, 999 and 917; since, the exam was multiple choice we were ...
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### 1 in, 1 out (The Security to the Party Maze)

A party is being held at a local mansion. The host is very rich and his success is because of one thing ~ his famous recipe for spaghetti! The spaghetti recipe is kept in a secret room inside the ...
265 views

### What should you substitute?

Find all functions $f:\mathbb{R}\rightarrow\mathbb{R}$ such that $$xf(x)-yf(y)=(x-y)f(x+y)$$ for all $x,y\in\mathbb{R}$. Problem by me. Most elegant solution gets the checkmark!
211 views

### Find the equation of this surface - The Snowman

Here is a surface that resembles a snowman: Its equation has the form $f(x,y,z)=0$: if a point $(x,y,z)$ satisfies that equations it is shaded, otherwise it is "left blank". Your goal is to find $f$. ...
264 views

### Fibonacci progression

In a number sequence, 1, 13, 169 and 2014 are respectively the first four terms of the sequence. The next terms are equal to the sum of the four numbers that precede them. For example, the fifth term ...
827 views

### An Evolutionary Experiment

Dr. Farnsworth entered class today and announced that we were going to conduct an experiment to see if we could force cells to evolve to communicate with us. The experiment is as follows: we are given ...
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### Maximise your gold!

You met a genie. He gets $150$ magic lamps out, which are numbered from $1$ to $150$. You have to colour each lamp red or blue. After colouring, the genie will count the number of triples $T$ of magic ...
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### n(n+1) as a multiple of 100

Here's a puzzle I came up with while walking today: For how many natural numbers $n$ is the number $n(n+1)$ a multiple of $100$? This is true for infinitely many $n$, so "how many" means something ...