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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3
votes
1answer
117 views

Find the first three terms of the sequence

Find the missing values in the sequence: $X, X, X, 59, 2, 65, 3, 58, 9, 79, 3, 23$ Hint 1: Hint 2:
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3answers
129 views

Find the next three terms in the sequence

This sequence consists of triplets; each triplet is linked to each other. $1,36,8,2,48,4,3,60,0,\text{X},\text{X},\text{X}$ The three $\text{X}$'s signify the missing numbers.
18
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2answers
2k views

We are two immediate neighbors who forged our own powers to form concatenated relationship. Who are we?

Our concatenated number is $ \overline{ABAC}, $ where $ A, B, C $ are all positive digits (1 - 9). Our relationship is $$ \overline{ABAC} = A^A + B^B + A^A + C^C $$ Who are we?
6
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1answer
138 views

Find the immediate square dancing neighbors, they dance together to perfect square

We live in a community of houses sequentially numbered from 1 to 100. We all love square dancing but only two immediate neighbors are joy to watch. If you concatenate their house numbers, it forms a ...
5
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2answers
651 views

Madam I m Adam..please don’t get mad..you will no longer be prime

Take away $ \overline{MAD} $ from $ \overline{MADMADAM} $ to make her prime. $ \overline{ADAM} $ is prime too if he does not get mad: $ \overline{MADADAM}. $ $ M, A, D $ are 3 distinct digits that ...
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3answers
470 views

Solve for the Number in the number..square..cube relationship

Each letter stands for a distinct digit...no computer or calculator needed. Just pure logic and some mental multiplication. CUBE is a concatenated number and it is a cube. X denotes multiplication. (...
9
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1answer
607 views

Narcissistic cube asks who are we?

I am a five digit narcissistic cube who likes to display my root right upfront. I also have hidden it in the back of my four digit cube brother. Who are we?
-1
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1answer
188 views

Can you find this abundant dad and his six prime sons?

We are six little prime brothers. All our ages add up to the age of our abundant and old dad who is obviously not in his prime. However, if you pair him up with either of the prime neighbors, they ...
19
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6answers
2k views

My Sixteen Friendly Students

I have sixteen students in my class who sit in four rows of four. Each week they sit in a different order. After a number of weeks every student has sat next to every other student, next meaning ...
18
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8answers
2k views

30 fake coins out of 99 coins

You are given 99 coins which consists of 30 fake ones. You also have a digital balance scale with perfect precision that shows how much difference between weighs you put on. For example, if you put 10 ...
-9
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1answer
104 views

Number of days in a normal year expressed with five consecutive positive integers [closed]

Given $D$ is the total number of days in a normal year $a$, $b$ are positive integers $P$, $Q$, $R$, $S$, $T$ are consecutive integers Figure them out by combining the following six expressions ...
13
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3answers
2k views

99 coins into the sacks

You have 99 coins that you need to place into any number of sacks. After doing so, you write on each one the number of sacks that are lighter than that sack. For example, if you put 98 coins into one ...
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2answers
158 views

Excellent Bike Riders. All under 100. Find the missing members marked x

Excellent Bike Riders. All under 100. Find the missing members marked x. They are all members of special club. 97 X 59 29 X 23 X 7 X
5
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2answers
197 views

SafeCracker #2 - The Mission Continues

Thanks to an alert StackE user, we were able to get the first safe open. Mission Details This next safe is in a former employee's house. He is gone for now, so we have no time to spare. We weren't ...
5
votes
1answer
129 views

Surviving the Zombie Apocalypse

It is the zombie apocalypse. Your car has limited fuel in it, and you will not be able to refill your tank once you run out. You are planning one final mission to gather supplies. You have identified ...
6
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1answer
208 views

XOR: Is it possible to get $a$ and $b$ if I have $a \oplus b$ and $a \times b$?

Intuitively I would say yes but I can't find a way to prove it. I tried with small values and bruteforcing shows that there seems to only be one solution given a distinct tuplet. For example $(1,72)$ ...
18
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5answers
863 views

Primes less than 100 in a 4 x 4 board

Place one of the digits (0 to 9) in each of the cells of a 4 x 4 board so that as many as possible of the 25 primes less than 100 divide at least one of 10 positive 4-digit numbers that can be read ...
0
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1answer
129 views

He said yes..she said no..they went back and forth..they agreed to [closed]

To call it a Prime. S, N, O are 3 distinct digits that are to be determined by you so that their conclusion is right Full concatenated number: SNOSNOS
-3
votes
1answer
230 views

Repeating decimal. 0.01234567901234

Express the repeating base-10 decimal number $ 0.0123456790123456790... $ as a fraction $ \dfrac{1}{x} $ in any base system up to hexadecimal such that $ x $ has a minimal number of only 0s and 1s.
2
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1answer
87 views

The NANNP Grid ( Not another Next Number Puzzle )

Simply figure out the last row...
0
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1answer
74 views

Place Your Bets 3 , last of the series

A harder sequence to figure out... What are the next 4 cards, including suits?
2
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1answer
84 views

Place Your Bets - in sequence, of course

Your Puzzle There is some sort of pattern in cards below. Simply figure out what the next card should be. Note: You cannot re-use a card already in play.
3
votes
2answers
90 views

A Wine Problem for Puzzlers [duplicate]

Simple Follow the instructions on the label. In case you the image is too small, Given three bottles: 8, 5 and 3 liters capacity, divide 8 liters in half (4 + 4 liters) with the minimum number of ...
0
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17answers
5k views

I’ve officially counted to infinity! [closed]

Sarah called me today and explained that she had counted to infinity. I shrugged and said it was impossible. She said that since I didn’t believe her, she would do it again, and this time in only ten ...
4
votes
1answer
792 views

Number of seconds in 6 weeks

Using only 3 characters (any single digit or one of the following operators: $ +,\, -,\, \times,\, \div,\, ! $), construct an expression that evaluates to the number of seconds in 6 weeks.
48
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11answers
252k views

6, the magic number

Here's a fun (albeit difficult) one: Make these equations true using arithmetic operations: ...
0
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1answer
91 views

Why do I always lose? [duplicate]

As always, good luck! Sarah is really good at math. I mean, really good at math. Every now and then we play this game where we take turns picking random numbers between 1 and 10, and we add these ...
7
votes
3answers
212 views

Groundhog Puzzle [duplicate]

A groundhog has made an infinite number of holes one metre apart in a straight line in both directions on an infinite plane. Every day it travels a fixed number of holes in one direction. A farmer ...
32
votes
18answers
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}\...
4
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6answers
2k views

Find 108 by using 3,4,6

Assemble a formula using the numbers $3$, $4$ and $6$ in any order to make 108. You may use the operations; $x + y$ $x - y$ $x \times y$ $x \div y$ $x!$ $\sqrt{x}$ $\sqrt[\leftroot{-2}\uproot{2}x]{...
13
votes
11answers
15k views

Combine 3, 3, 5 & 7 to get 24

Using operators plus, minus, multiplied by and divide by, and as many brackets as you want, can you do a formula which uses 3, 3, 5 and 7 to make 24? Each number must be used and can only be used ...
18
votes
9answers
1k views

One-one communication

5 people are standing in a circle - person A needs to tell his salary to person B, but none of the others should know A's salary. How is this possible, if every person only whispers to the person on ...
6
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4answers
584 views

Puzzling Equations

Mathematics is a fascinating field of study, ever changing, far from finished. Arbitrary symbols, prescribed with special meaning become extraordinary challenges for the mind. And if you’re like ...
6
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2answers
182 views

Just a Simple Number Crossword

I made a small number crossword for my mathletes club that I thought I'd share. It's not too hard, I think it's just right for a coffee break. Have fun! (Edit: No answer has a leading zero)
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15answers
5k views

What is ls Largest Number Formed by only moving two sticks in 508?

Tilting the Image is not allowed. You can cannot change order of digits. You cannot change the Size if Digits unless you are harry potter. You can increase or decrease space between digits though. ...
0
votes
1answer
129 views

How much did he pay for the car? [closed]

A man withdrew half the money that was in his bank account to buy a second-hand car, then sold the car two weeks later, receiving only three-quarters of the price he had paid for it. When he paid the ...
6
votes
1answer
198 views

What kind of puzzle this is?

I received this picture, and the sender told me that it means something?
4
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3answers
788 views

Scheduling based problem

Can you place these numbers into 5 rows of 4 such that each row totals 20? 1, 2, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 6, 6, 7, 8, 8, 8
3
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3answers
459 views

What are the fewest weights you need to balance any weight from a triangular seesaw?

I saw this question: What's the fewest weights you need to balance any weight from 1 to 40 pounds? Suppose you want to create a set of weights so that any object with an integer weight from ...
31
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4answers
4k views

Happy pi day, everyone!

A baker is working a batch of dough. He shapes it into a cylinder of height a and radius z. What will the baker make from this volume of dough?
0
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1answer
194 views

Fastest Way To 6 Pawns On the B To H Files

MASSIVE UPDATE: I decided to play around with this again today, and I found MAJOR improvmemts for the B to G file games. See if you can beat me! If not, give proof as to why my game is optimal (To ...
0
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2answers
100 views

Max pieces to cover a chess board [closed]

Number of individual chess pieces to cover all chess board
4
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2answers
238 views

100 prisoners' names in boxes, against smart warden

My question, which I do not know the answer to, concerns the classic 100 prisoners and 100 boxes puzzle, summarized below. The solution to this assumes the names are placed in boxes randomly, and gets ...
1
vote
2answers
330 views

The result is 7 game

The goal of this game is to find the lowest score for the 10 equations below. 0 ? 0 ? 0 ?...
1
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6answers
407 views

Product of Factorials

In the annual meeting of the International Conference of Puzzle Scenarios, each of $100$ people in a room is given a different number from the set $\{1!,2!,3!,...,99!,100!\}$. One person leaves the ...
0
votes
1answer
98 views

Arranging people in groups at a conference

54 people attend a conference. There are 6 tables that each seat 9 people. Each table has a different topic and all 54 people have to move around and sit at each table. Can you advise a formula as ...
-2
votes
1answer
198 views

How to solve this puzzling?

20190309,245111132328,331508165892,51222189610023,? A friend of mine gave me this number puzzling but I have no idea what is the logic. Does anyone know how to solve?
5
votes
2answers
151 views

Bracket schedule

my friends and I are doing beer Olympics. There are 12 teams with 6 games. Each game has its own “bracket”. Essentially there will be 6 winners, 1 from each bracket or game. Those teams will then ...
26
votes
9answers
8k views

A clock for 2017

Design a clock where each number from 1 to 12 is obtained as an arithmetical operation using each digit of 2017 exactly once: for example, 4 could be made as $2\times 7-10$.
41
votes
4answers
2k views

Hamlet and the theatre

Hamlet is preparing a play to find out the truth about his father's death. The theatre has $2015$ numbered seats and can contain all the members of King Claudius's court. He gives to each member a ...