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Questions tagged [logical-deduction]

A puzzle that needs formal logical deduction to arrive at a solution.

17
votes
5answers
1k views

Again! 6 prisoners, 2 colors, one mute

After that last game, the warden didn't like that they escaped. So he made them all play again. Like before, they know there are 6 prisoners, 3 red hats and 3 white hats. They know one prisoner is ...
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 ...
6
votes
1answer
189 views

Get 20 points from a target board

A target board consists of four parts, and each part has different numbers on it. You will make at most $10$ shots, and every shot's point will be added to your score. If you get a score of $20$ ...
34
votes
13answers
7k views

6 prisoners, 2 colors, one mute

Just like the classic 4 prisoners hats riddle, here we have 6 prisoners buried to their necks in the ground. They can only look straight ahead so that A only sees B, C, D, E while B sees C, D, E, and ...
0
votes
1answer
102 views

The mystery of the lost coin [duplicate]

Three travellers are on the road. As the day comes to an end, they pass through a village and agree they should stay here for the night. As luck would have it, the Brown Bear Inn is just down the road....
0
votes
2answers
115 views

Figure sequence 2 [closed]

Can somebody explain why C is the correct answer?
2
votes
1answer
155 views

Hexagon in a circle

Similar and Hint to: Dodecagon in a big circle There are $6$ bars which comprise two groups of $3$, $3$: each group has identical bars but every group has a distinct length of bars. For example; ...
3
votes
1answer
158 views

Dodecagon in a big circle

There are $12$ bars which comprise three groups of $6$, $3$ and $3$: each group has identical bars but every group has a distinct length of bars. For example; Group 1 may consist of six ...
7
votes
1answer
154 views

Class Seating Arrangement

There are $25$ students with distinct heights in a class. The seats are arranged in the class like a square array ($5$x$5$) and students are seated such a way that each person will be taller than both ...
2
votes
1answer
143 views

Puzzle #7: Thrown for a Loupe

Five magnifying glasses have been laid out on a table. Let's call them A, B, C, D, and E, with A on the left, B next to it, and so on. The lenses have different magnifications, these being 2x, 4x, 8x, ...
0
votes
2answers
95 views

What A Crazy Night

Having decided to accept an invitation to a party, you arrive at midnight in full dress. However, inside the mansion is a scene of madness. across the Hall, a Star flings a Cup of Water at an ...
-4
votes
3answers
122 views

Riddle Again, Riddle Again, What am I? [closed]

1. If a chicken says, "All chickens are liars" is the chicken telling the truth? 2. A man is traveling to a town and comes to a fork in the road. If he goes left, he goes to the liars' village....
9
votes
7answers
383 views

3 travelers and 9 diamonds

I think this is the most appropriate place to share this. I haven't figured out the answer yet, but I think I'm close. I couldn't find anything like this on the Internet, so I'm posting it here. ...
4
votes
5answers
2k views

What is her real age? [closed]

He : What is your age? She : 35 years old, ignoring the intervening Saturdays and Sundays. What is her real age?
19
votes
3answers
2k views

Which two houses didn't get any mail that week?

Postman delivers the mail in the small village. This village has exactly ten houses, numbered from 1 to 10. In a certain week, he did not deliver any mail at two houses in the village but at ...
12
votes
3answers
749 views

Sticky sticky stick stick

You are given a long enough stick. Your task is to create a new type of foldable ruler something like shown below with it by cutting the stick into pieces and folding them at one point: You need to ...
1
vote
2answers
147 views

Logical confusion

This time, there are 20 questions, no bold or strike or anything. Just the puzzle. In #12, another way of saying it is that 10 statements are true. If you don't want to do that, provide a concrete ...
6
votes
4answers
212 views

A Space Station 13 malfunctioning A.I

Disclaimer: It is not necessary to read the previous puzzle, or the one before even if it continues on the same story. The current puzzle is a different one which can work as a pure standalone. ...
4
votes
11answers
4k views

Who killed the husband? [duplicate]

There is a round house with only one room. There is a maid who does everything, a butler who usually gets the mail, an annoying husband, and a lazy wife in the house. The husband is murdered ...
4
votes
2answers
240 views

What Kind Of Test Is This?

One day, a teacher decided to give unusual multiple test questions to the students. They were all surprised at the questions and none of them got anything correct. Can you help them? Questions : ...
14
votes
5answers
4k views

I'm a seven letter word. What am I?

I'm a seven letter word. My first three letter stands for animal name. My 2nd, 3rd, 4th, and 5th letter stands for food. My 4th, 5th, and 6th stands for utensil. My 5th, 6th, and ...
-4
votes
2answers
83 views

Find the missing entity: [closed]

Ao, Eo, Io, _ ? _, Uo What is the missing entity. Provide the reasoning to back up your answer. I have considered Oo already but that doesn't seem to be the required solution. Please help.
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 ...
4
votes
1answer
104 views

Pictogram using musical notation

Rebuses: they're music to my eyes.
12
votes
3answers
354 views

True or Faulse?

There are lots of easy questions: How many colors are in a rainbow? How much do 2018 pennies cost? Why did I add an extra letter to 'false'? However, this riddle, is not one of those. You are to ...
4
votes
2answers
120 views

#4 Sheepish Rebus

Not trying to pull the wool over your eyes...
4
votes
1answer
76 views

Pictogram Teaser

These guys wish they could have what they symbolize...
3
votes
1answer
92 views

Another rebus for your brain aerobics

This is a saying from an ancient book (a saying Scrooge probably hated, prior to his turn-about):
3
votes
3answers
173 views

99 Coins among 9 pirates [duplicate]

Nine Pirates are splitting 99 gold coins among them. Each of them has already one extra gold coin in their pockets. Starting from 1st pirate, each will make a proposal on how many coins will be given ...
7
votes
3answers
402 views

Rectangular Prisms

Eight corner bricks are taken out from a 5x5x5 block, which is something like below: How many rectangular prisms of all sizes can be counted in this block? Source: Oyun 2018 Final Exam Question
3
votes
1answer
110 views

Inner Triangles in the circle

$18$ points are selected on the circumference of a circle, all of which are connected to each other by straight lines. If no three lines intersect at a common point, What is the number of a ...
8
votes
1answer
165 views

First attempt at a rebus

See if you can decipher this image:
6
votes
3answers
222 views

Oddy Chessboard

On a standard chessboard, What is the number of different arrangements of pawns such that every square has an odd number of pawns on its neighbor (horizontally or vertically) squares? Note: ...
1
vote
3answers
142 views

Too many Circles

Using 20 Circles, what is the maximum number of intersecting point that can be obtained? For example, if there were 3 circles, the answer would be $6$ as shown below:
1
vote
3answers
287 views

Not Your Regular Chess Challenge

Imagine that you have a normal 8x8 chessboard and you have an unlimited amount of all kinds of chess pieces. Find the greatest and lowest number of pieces you can have in that chessboard without those ...
2
votes
5answers
347 views

A Very Odd Game

Barry, John, and Caleb, all perfect logicians, were very bored one day and they decided to come up with a new game (they haven't got a name for that game yet). The rules were quite simple : The first ...
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 ...
0
votes
1answer
151 views

Tourist logic destination

There is logic to the numbers of tourists who visited these places one day. How many tourists went to Denver that day and how are the numbers worked out? ...
13
votes
2answers
945 views

How many questions in the exam?

A group of students have taken an exam. We have the following information: Every student answered at most 15 questions. Every question is answered by at least 1 and at most 3 students. Every three ...
3
votes
2answers
153 views

Number of Students in the class?

Each student writes down his/her name, surname, age and birthplace on a card in a class. After that, these cards (each containing four entries) are collected and examined. The following observations ...
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. ...
5
votes
2answers
448 views

Video Game Explanations in 10 Words or Less

So, my friends and I came up with a new type of puzzle similar to that of the Every _____ Movie Reviewed in 10 Words or Less, in which movies are reviewed in 10 words or less. So my friends took this ...
5
votes
1answer
310 views

A Stick and Two Similar Triangles

You have X centimeters of a straight stick. You divide this stick into 4 pieces. All sticks have distinct integer centimeters lengths. After that you form a triangle, then take one of the stick of ...
1
vote
3answers
275 views

Form Common Geometric Shapes

You are given 1,000,000 units of straight thin stick and your task is to create one triangle, one square, one rectangle by cutting the stick into sides. None of the side of each shape has common ...
2
votes
1answer
184 views

Find 93 using first 4 prime numbers

Using operators plus (+), minus (-), multiplication (x) and division (/), power function/exponentiation (^) and as many brackets as you want, can you find A formula which uses 2,3,5,7 to make 93?
5
votes
3answers
254 views

Weirdly Numbered Cars

There is a car race where there will be a couple of cars and the cars are numbered from $1$ to $X$, not necessarily incrementally but all distinct positive integers. But strangely all possible sums of ...
3
votes
1answer
210 views

Who is your secret santa?

My first puzzle question here. I hope this meets your quality standards. :-) First a short anecdote about the puzzle, that has no relevance if you just want to solve it: Over a number of years, I was ...
4
votes
3answers
675 views

Eleven divided by two is two, and two plus four is seven. This is proven, it is as true as two equals three

Seemingly the title went unnoticed, it has some important logic: ...
9
votes
1answer
487 views

Moving 4 sticks to form 8 equilateral triangles

We have $6$ thin sticks with the same length parallel to each other shown below: The distance between neighbor sticks are unknown and for sure smaller than half the length of the sticks themselves as ...