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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.

9
votes
6answers
1k views

Distinct digits but Close Enough

Using the digits from $1$ to $9$, Form four numbers, such as ($X$,$Y$,$Z$,$T$) Then take $X\div Y$ and $Z\div T$ where both values should be different than each other. You need to use all digits ...
9
votes
1answer
286 views

Form the biggest squaring number

You are going to start from any number with distinct digits lower than four digits (such as $a$, $ab$, $abc$) and you will apply the rule below: Take the square any number you want in the number (you ...
7
votes
2answers
228 views

A natural system of equations

What goes in the question mark? (Same for both equations). It is something very well-known. Hint:
1
vote
2answers
147 views

Move something in the equation

$1484 / (7 / 9) = 19$ Make the equation true by moving one continuous shape or operation in the equation. (You are NOT allowed to make an inequality or equality sign or touch the = sign.) You can‘t ...
1
vote
4answers
234 views

Only one change to be made

Your objective is to change one constant in the following equation so that it equates to true. Rules: No changing the equals sign. The numbers are correct. There only needs to be one change in order ...
6
votes
2answers
424 views

2019 is coming!

Use $2$ $0$ $1 $ and $9$ to make the numbers $66, 74, 76, and$ $77$ RULES You must use all 4 digits. Only the digits 2, 0, 1, and 9 can be used. You can make multi-digit numbers out of the numbers. ...
-1
votes
14answers
2k views

Move one thing in the equation [closed]

$1484 / (7 / 9) = 19$ Make the equation true by moving one continuous shape or operation in the equation.
11
votes
8answers
2k views

No love for 2 and 3

Form two numbers. The sum of them must be $100$. For the first one you must use the digits $4$, $5$ and $6$ taken exactly once in this order. You cannot use other digits. For the second one you must ...
2
votes
6answers
244 views

A Maximising Puzzle Gift for my Girlfriend and I's 28th month Anniversary

The 28th of december 2018 will exactly be the 28th month since I date my fabulous girlfriend, by this time she'll be 18 years old. Here's a puzzle I'll give her this day : Classical part Maximize $...
7
votes
2answers
206 views

Simple Arithmetic Puzzle 6. Or is it?

Here's a sixth one! (with a twist) \begin{align}16&=\boxed9\times18\\5&=13\times\boxed3\\?&=9\times20\end{align} Can you find the value of the question mark? HINT 1:
31
votes
17answers
11k views

Use 2, 0, 1 and 8 to make 109

Assemble a formula using the numbers $2$, $0$, $1$, and $8$ in any order that equals 109. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\sqrt{x}$, $\sqrt[\leftroot{-2}\...
-2
votes
2answers
118 views

How many are they, how much do you owe them? [closed]

Let's suppose you want to build a house. To do this, you're going to need people to help build the house. Specifically, you're going to need contractors, engineers, and construction workers. After ...
5
votes
3answers
940 views

How many apples should you carry? [duplicate]

You are on your way to your friend's house. You decide to carry 2 apples to your friend. To get to their house, you must pass across 8 gates. At each gate, the keeper will take half the amount of ...
1
vote
1answer
104 views

Find the next number in order [closed]

Find the next number in the sequence 9, 73, 241, 561, 1081, 1849,____
3
votes
1answer
143 views

Move one shape in the equation [closed]

$1484 / (7 / 9) = 19$ Make the equation true by moving one continuous shape or operation in the equation.
4
votes
2answers
714 views

Use 2, 0, 1 and 8 to make 71

Use all and only the digits $2,0,1,8$ once each to make the number $71$. Allowed operations; anything not on this list is banned: $+,-,\times,\div, ()$ (parentheses and/or choose function) ...
14
votes
6answers
2k views

Use 2 0 1 and 8 to make 67

Use $2$ $0$ $1 $ and $8$ to make the number $67$ RULES You must use all 4 digits. Only the digits 2, 0, 1, and 8 can be used. You can make multi-digit numbers out of the numbers. Examples: 20, 82, ...
6
votes
8answers
498 views

Make $1,\dots,15$ using $3, 9, 9, 9$

This was inspired by many puzzles that use three/four numbers to create other numbers. I chose these numbers in particular because of this post. Can you find a way to make all the natural numbers ...
0
votes
2answers
76 views

A maths function

I am using a function, and the outputs are below. What function am I using? function($0+0$) = 0 function($73942856-628529469252$) = -1 function($1 + 1$) = 1 function($1+2$) = 1 function($528^0$) =...
4
votes
3answers
171 views

Fix the perfectly ordered equation

This question is follow up to Something is wrong with the equation This time our numbers are given as below included each numbers on a keyboard order and some basic math operators next to each other ...
57
votes
24answers
17k views

Make 0 0 0 0 = 8

Can you find a way to make: $0\ 0 \ 0 \ 0 = 8$ by adding any operations or symbols? You can use only these symbols: $+,\ -,\ *,\ !,\ /,\ \hat\, ,\ ()$. It is limited to this list, and ...
9
votes
3answers
332 views

Something is wrong with the equation

There is something wrong with the equation below: By just exchanging two squares at a time, find the equality with the least amount of exchange. For example if this question is asked for below ...
8
votes
4answers
801 views

Mathematical puzzle: ten digit lock number

A mathematical professor set his lock number, he used mathematics so he would remember the ten digit code. He used all of the numbers from 0-9, every number only once. In his mind the first two ...
23
votes
1answer
3k views

Maths equation: 357568588-11 = ~357568584.858

Move one line and make this true: $357568588-11 = $ ~ $357568584.858...$ No cross through the "=" sign stuff. Hint:
3
votes
2answers
127 views

Puzzle #6: Brain Coaster

A carnie who is an extreme fan of mathematics was asked a strange question by a university student. The student asked how many rides were there total in this amusement park. The carnie, being polite, ...
0
votes
0answers
43 views

Help me visit my friend through his new digital key lock [duplicate]

A friend of mine whom I have repeatedly tried to visit has upgraded his house‘s security system. Instead of using doorkeys which were quite easy to borrow, he‘s using one of these fancy new electric ...
4
votes
2answers
110 views

A story reminiscent of something

An old Russian mathematician once told me this strange story... “In a galaxy far away there is a civilized species. The skin colors of everyone in the species is blue or green. Among the ...
15
votes
7answers
4k views

Make 4 4 4 4 = 30,31

Follow up question to Make 5 5 5 5 = 19 Can you find a way to make: $4\ 4 \ 4 \ 4 = 30$ and $4\ 4 \ 4 \ 4 = 31$ by adding any operations or symbols on the left side of the equations? You can ...
8
votes
5answers
786 views

Find the word with the highest normalized product of letter-prime values where A=2, B=3, C=5, …, Z=101

Which word has the highest normalized score according to the following: Assign each individual letter A..Z of an (English) word a value corresponding to the n'th prime (see table below). Take the ...
10
votes
6answers
2k views

Maximize the number of factorials in your solution to 6 5 4 3 = 1

Using the same rules as Make 6 5 4 3 = 1, but maximize the number of factorials. You may not take the factorial of 1 or 2. This is harder than it looks. A great answer has six factorials, an ...
11
votes
12answers
8k views

Make 6 5 4 3 = 81

Can you find a way to make: 6 5 4 3 = 81 by concatenation and/or adding any of (and only) these mathematical operators: + - × ! ÷ ^ standard parentheses () You cannot add other numbers to the ...
4
votes
9answers
1k views

Make 6 5 4 3 = 1

Can you find a way to make: 6 5 4 3 = 1 by concatenation and/or adding any of (and only) these mathematical operators: + - × ! ÷ ^ standard parentheses () You cannot add other numbers to the ...
22
votes
10answers
13k views

Make 5 5 5 5 = 19 [closed]

Can you find a way to make: $5\ 5 \ 5 \ 5 = 19$ by adding any operations or symbols? You can use only these symbols: $+,\ -,\ *,\ !,\ /,\ \hat\, ,\ ()$. It is limited to this list, and ...
4
votes
3answers
310 views

Gotta Catch 'Em All!

As I got ready for work today, I had my television on Netflix as I always do. See, the thing about Netflix, they auto-play trailers for the item that is currently in focus. Well, after starting my ...
36
votes
10answers
5k views

Unsolved Maths Problems as Puzzles

On an internal wiki at work, people sometime post puzzles similar to those found on this website. Most of the questions are formulated as a story or word problems, but can be expressed mathematically ...
8
votes
1answer
205 views

Create your own custom ruler

There is a blank ruler of $X$ units. You are going to set $9$ marks on this ruler so that you will be able to measure all integer values from $1$ to $X$ units with only one measurement. What is the ...
1
vote
4answers
122 views

Mathematical Mystery 4

Known by 2 names, argued by ways One of them sounds irregular, sometimes that pays My legs are like a human's, usually alike This is easy, known by a child's psyche Name the mathematical ...
5
votes
3answers
186 views

Some things are best said in plain language instead of mathematical notation!

Back then in 2013 when I was participating in International Olympiad in Informatics (IOI), I was stumbled on the puzzles on their newsletters. Even until now, I'm pretty clueless for these. Here are ...
11
votes
4answers
2k views

Alien Number System

An alien civilization has a strange way of notating their numbers. Here are the first 30 numbers in their system: The notation is unique up to slight differences in handwriting. Therefore you may ...
-5
votes
1answer
137 views

Making 49 from 5, 1, 3, 4 [closed]

I have these numbers: 5, 1, 3, 4. There are four different ways to make 49 - what are they?
1
vote
2answers
320 views

A Secret Math Society

I was about to try to join the famous Math club at my school when I stopped to hear my classmates doing the same. I didn't know that newcomers had to take a simple test to be qualified until my they ...
3
votes
2answers
229 views

Cut cut cut… the rope!

I have a rope and I cut it into two different integer lengths and gave one of them to Alice, the other one to Bob. Then I asked Alice and Bob to cut their ropes into pieces in such a way that when ...
11
votes
1answer
594 views

What a weird final exam

someday, some math teacher decided to test the logic deduction capacity of the class consists of 32 students. When the class began, he showed a letter to each student between A to E and said: "There ...
5
votes
1answer
171 views

Another pattern puzzle with a twist…well, not quite so

What are the next two terms of the following crazy sequence: I, h, 6, 9l, 52, 9E, 6h, __, __ ?
0
votes
2answers
201 views

Just another simple math problem

$4+5=9$ $7+9=13$ $11-5=9$ $17+29=\,?$ Find the value of "?"
3
votes
1answer
106 views

Mathematical Mystery 1

I come before V when I open up to you You focus on a point and get directed to a line too My cone isn't delicious to many a high schooler If only compared to hyperbolic humor I was cooler Name ...
12
votes
3answers
2k views

Removing 100 digits from the first 100 numbers

Write the first 100 positive integers next to each other to form one big number: $$123456789101112131415161718192021\dots90919293949596979899100.$$ If we remove 100 digits (not necessarily consecutive)...
0
votes
0answers
42 views

Find a specific permutation of { 0,…,9 } [duplicate]

Please arrange the ten digits 0,...,9 in a sequence abcdefghij, such that: Each digit appears once and only once. The number 'a' is a multiple of 1 The number 'ab' is a multiple of 2 The number '...
13
votes
4answers
336 views

20-Questions on a grid

Posted this on /r/puzzles too, none have given the right strategy as of now :) There is a square grid of width and height $m$. Three facts about the grid: Each cell has a value, and no two cells ...
14
votes
3answers
2k views

How many smurfs are there?

Papa Smurf gathered some berries from the forest to the village and smurfs ate all those berries: The smurf who ate the most actually ate one-fourth of the berries eaten by the rest of the smurfs. ...