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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.

3
votes
3answers
293 views

Grandpa's Numbers

Grandpa likes pencils but not pens Grandpa likes Beijing but not Tokyo Grandpa likes math but not chemistry Grandpa likes Contact but not _______ Make sure to explain! Hint 1: Hint 2:
1
vote
4answers
277 views

The evil genius infinite plan

I'm an evil genius and I'll conquer the world with my minions :] My minions have just 2 egdes but in just 2 minutes I've produced an infinite amount of them. You'll see how I will conquer the world- ...
4
votes
1answer
302 views

The triangle-sequence riddle

this is my number sequence: / - / - 1 - 2 - 7 - 6 - ? This riddle has somtething to do with equilateral triangles Good luck and have fun :) PS: please tell me if this is too broad, this is ...
8
votes
2answers
894 views

Mystery at the Arcade

7 people, A-G, were competing in the national championships of the new arcade game Corpse Deems Us. They each scored a whole number of points from 1 to 100 inclusive, but it wasn't clear what the ...
6
votes
2answers
2k views

100 Fruits for 100 Dollars a more challenging version

This is a more challenging version of the reported puzzle " How will you get 100 fruits in Rs. 100? " Bob buys 4 different fruits for exactly 100 dollars Jackfruits cost 15 dollars each ...
5
votes
5answers
403 views

Time-Motion puzzle

Time and Motion studies are well established. Here is an easy question: It takes 8 men 6 months to build 2 houses at a cost of $50,000. It takes 10 men 5 months to build 3 houses at a cost of ...
6
votes
1answer
352 views

I have a puzzle and a solution… it's the method I'm after

The cipher message is: J B A Z R X K Z N T W K O Y E Z The answer is: T O N G L A N D B R I D G E How did I (or more accurately my father) arrive at the answer?
13
votes
1answer
728 views

My Social Security Card Number

I have forgotten my social security card number. All I remember is that it is the largest integer with the property that the block of any two of its digits that are adjacent is either a two-digit ...
-6
votes
1answer
146 views

100 birds 100 rupies. parrot cost is 5rs, crow cost is 1rs and sparrow cost is 0.05paisa please solve this? [closed]

100 birds 100 rupees. parrot cost is 5 rs, crow cost is 1 rs and sparrow cost is 0.05 paisa. all 3 birds are required. please solve i want 100 birds on 100 rs.
9
votes
4answers
428 views

Cupcake division

A elementary school student brought cupcakes to their class to celebrate their birthday! However, there's a problem: There are 25 students in the classroom, and only 24 cupcakes! The students have ...
6
votes
2answers
467 views

I love baking, do you too?

I love programming, it's so fun Just get every computer in the world And just do program as much as you can Because with everyone on your side you can never go wrong with programming And no, ...
8
votes
4answers
969 views

A Mix of Puzzles

Weapon of the sea, undented, times x or y minus the first, reversed. 3-4 triangle complete. A bucky lemur nun. Shakespearean poem less nonagon's sides. Krypton minus vanadium. (omg ...
4
votes
3answers
200 views

Lots of children with Halloween candies

You are a teacher in a big kindergarden and halloween was just yesterday. You decided to put the children into a candy race by dividing them into 19 groups to gather candies from houses nearby (they ...
12
votes
3answers
1k views

The thought of my prefix brings many a smile; My infix is, mathematically

Here's my first attempt at a Riley! Good luck! The thought of my prefix brings many a smile; Sit down, relax, or sleep for a while. My infix is, mathematically; One point six times ...
-4
votes
1answer
114 views

The unthinkable sequence

To correctly answer this question, I would like you to include the next 5 numbers of this sequence and also tell me why they are the correct numbers. 3, 4, 8, 9, 14, 23, 25, 31, 36, ?, ?, ?, ?, ? I ...
9
votes
3answers
253 views

The END (Riley riddle)

My prefix you say in astonishment, My infix within the prefix slightly smaller than a pie My suffix is huge, or even enormous, And here comes the end of the riddle. Hint 1:
6
votes
2answers
179 views

Number sequence solving strategies

Number sequences are one of the oldest puzzle categories in the book. You would find it hard to look through a days worth of puzzles posted here and to not find any puzzles that involve some sort of ...
9
votes
5answers
650 views

The Three Kings of Metsyssisab

In the world of Metsyssisab, there were three kingdoms, ruled by King Owt, King Eerht, and King Ruof. One day, a fourth, evil king, King Evif, who ruled a small island, looked to control all of the ...
27
votes
6answers
7k views

Noughty Mathematics Question

Use your imagination to follow these instructions: Take out an imaginary piece of paper. Turn it 90° clockwise. Make a mental note to use right-justification and nice, tight kerning and leading. In ...
0
votes
3answers
120 views

Smallest positive integer divisible by $1$ to $100$ [closed]

What is the smallest smallest positive integer $n$ such that $n$ is divisible by $1$ to $100$ and $n$ is not $0$?
-2
votes
1answer
80 views

Complete the sequence if a specific pattern is followed [closed]

1, 4, 9, 18, 35, _ Find the next number if the occurence of numbers follows a specific order
1
vote
0answers
86 views

Hard Questions About Circles and Polygons [closed]

a circle has 1500 chords draw in it so that the maximum number of non overlapping regions is obtained. find the difference between the number of points of intersection of the chords and the number of ...
3
votes
1answer
131 views

This four-by-four Magic Square uses all the integers from -7 to 8. Complete the square. More Magic Squares!

This four-by-four Magic Square uses all the integers from -7 to 8. Complete the square. This is what has been given so far: -7 _ _ _ _ -2 _ +1 _ _ +3 _ +5 _ _ _ Please Help. Thank you
9
votes
3answers
330 views

Special triangles in convex polygons

Given identical 30-60-90 triangles, what is the convex polygon with the highest number of sides that I can build from them? This seems a very easy task by first look, but I’m totally stuck right now. ...
14
votes
2answers
340 views

The Number Guessing Game

Two people are playing an interesting form of a number guessing game, with the following rules: One person is the guesser, and one person is the thinker. The thinker thinks of a number from 1 ...
5
votes
4answers
213 views

Coin Removal Variation

A variation on this problem, where coins can become neighbors. There is a line of $n$ coins on the table, all showing either heads or tails. The object of the puzzle is to remove all the coins by a ...
10
votes
1answer
863 views

Fill in the number. Not as straight as it looks

The square below is missing a number: You have four options: 32 4 16 22 Please explain your answer. HINT:
1
vote
1answer
80 views

Create a 3x3 Magic Square that uses integers from -10 to -2

I've never used this before but i'm having trouble with this. Create a 3x3 Magic Square that uses integers from -10 to -2. By the way, this is a weird magic square since diagonals don't need to ...
14
votes
9answers
7k views

Salesman's claim for mechanical keypad lock - 5 buttons and 545 combinations!

A company makes mechanical keypad locks. The keypad is a set of five buttons arranged vertically. O O O O O The buttons are quite close together. Once a ...
11
votes
3answers
2k views

Coin removal problem

I have a slight variation of the coin flipping problem. There is a line of $n$ coins on the table; some of them are heads up and the rest are tails up, in no particular order. The object of the ...
1
vote
2answers
124 views

5 subjects and their marks

The following partially-filled table shows the marks scored by 5 students named A, B, C, D and E in five different subjects, namely P, C, M, B and S. The marks scored by all students in all subjects ...
3
votes
1answer
84 views

Creating my climbing wall

[based on a true story] I have here some climbing holds that I've made. There are two relevant parameters: The angle on the top, and The thickness, as shown. Now it is definitely the case that $...
0
votes
1answer
124 views

puzzling one for my 11 year old and myself [closed]

$\frac{1}{4}$ of the marbles in a box are blue. There are $24$ more red marbles than blue marbles in the box. The remaining $32$ marbles are yellow. How many red marbles are in the box?
2
votes
0answers
71 views

Sets and subsets [closed]

Assume a set of numbers $S$ which must satisfy four conditions. (1) Partition this set $S$ into three subsets $U_1$, $U_2$, and $U_3$ such that the sum of the largest subset is as small as possible (...
-1
votes
2answers
148 views

Who joined when?

An institute runs batches training students in C#. A new batch starts on the 1st of every month and every batch lasts for exactly 3 months (thus at any given time, the students of exactly 3 batches ...
32
votes
2answers
587 views

lolcatz can haz ur infinit cheeseboard

This is a problem on an infinite chessboard with pieces called lolcatz. They can move like queens or knightriders, but have a strange disadvantage... ... you've never heard of knightriders? Well, ...
5
votes
3answers
159 views

Buzz Buzz Busy Male Bees

A male bee is born from an unfertilized egg, a female bee from a fertilized egg. In other words, a male bee has only a mother, whereas a female bee has a mother and a father. How many total ancestors ...
7
votes
3answers
621 views

No spanish required

Each letter represents a digit, so what is Mucho and Poco (although who's to say?) ...
-2
votes
2answers
73 views

Schedule of a business [closed]

With a group of 8 students you have set up a small business with which you help a customer every day during the holidays to clean up his computer and to redecorate it. For the next day there are 12 ...
-1
votes
1answer
220 views

Why does 12/2 = 7? [duplicate]

Here's a quickie while I work on the fourth floor of the Puzzle Dungeon. It's going to be here within the next two days, probably. Find a way to divide 12 by 2 so you get 7. There are several rules: ...
6
votes
1answer
126 views

The town of Concentrië

Here you see a water map of the town of Concentrië. There are eight channels that run from the central boathouse of the city in a star shape. There are three canals that lie concentric around the ...
11
votes
3answers
815 views

The 1-expression

A "1-expression" is a formula in which you add ($+$) or multiply ($\times$) the number 1 any number of times to create a natural number. Parentheses are allowed. For example, you can create $22$ as ...
2
votes
15answers
3k views

Just One Line! Really? [closed]

Add ONLY ONE line (does not have to be a straight horizontal line or in other words, doesn't need to be an axis aligned to the equal sign) to make the equation below true : EQUATION : $...
5
votes
4answers
434 views

Grandpa’s baseball cards [closed]

One day at a family reunion we found a bunch of baseball cards in Grandpa's basement. Grandpa said we could split them among all the grandkids. There were 5040 cards in all, so each of us got a lot of ...
-1
votes
1answer
120 views

Residential society [closed]

In a residential society, there are 120 people who either consume only tea or only coffee. Of those 120 people, 25 are children (which includes male as well as female children), and 78 consume tea. ...
0
votes
2answers
116 views

Ranking And Average

Four athletes A, B, C and D are evaluated on four different parameters – S, A, I and T. Further it is known that: I. Each athlete was given a score, which was an integer between 4 and 10 (both ...
3
votes
1answer
287 views

It's almost a cube

What is the next number in this sequence? 7, 10, 12, 19, 20, 30, _____ Note: I added another number as at first the pattern fit this too well. Hint 1:
1
vote
1answer
183 views

Voting System Puzzle

Answer Questions 79 to 82 on the basis of the information given below: The year is 2089. Beijing, London, New York, and Paris are in contention to host the 2096 Olympics. The eventual winner is ...
4
votes
1answer
121 views

Length of the Sequence

There's a lot of number sequence based questions on this site. So I'm going to mix it up a little bit. This sequence will repeat eventually. You need to find how many numbers are in the sequence ...
5
votes
1answer
440 views

Solve this puzzle. I created for my friend for FUN :)

My friend is very good at puzzles. so i thought of creating one by myself and try to see if he can solve. Finally I succeeded and he gave up. Interested people can try. Hint: use all four arithmetic ...