# Questions tagged [logical-deduction]

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

1,744 questions
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 ...
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 ...
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 $20$ ...
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 ...
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....
115 views

### Figure sequence 2 [closed]

Can somebody explain why C is the correct answer?
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; ...
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 ...
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 ...
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, ...
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 ...
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....
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. ...
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?
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 ...
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 ...
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 ...
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. ...
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 ...
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 : ...
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 ...
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.
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 ...
104 views

### Pictogram using musical notation

Rebuses: they're music to my eyes.
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 ...
120 views

### #4 Sheepish Rebus

Not trying to pull the wool over your eyes...
76 views

### Pictogram Teaser

These guys wish they could have what they symbolize...
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):
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 ...
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
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 ...
165 views

### First attempt at a rebus

See if you can decipher this image:
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: ...
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:
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 ...
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 ...
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 ...
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 ...
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? ...
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 ...
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 ...
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. ...
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 ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...