# Questions tagged [logical-deduction]

A puzzle that requires formal logical deduction to arrive at the solution. This suggests more than merely reasoning through clues to find an answer (you might want [situation] for that).

1,903 questions
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### Tiling a square with rectangles

Tile completely this 47 x 47 square with 52 rectangles. Each rectangle must contain precisely one numbered cell, and that number must be the area or perimeter of the rectangle it finds itself in.
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### Missing informations for the architect

An architect wants to plan the creation of a house, but he has only two perspectives, one from the left and one from the front. The house consists of concrete cubes. All concrete cubes must be ...
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### Fill 5 x 5 grid

In each cell of a 5 × 5 square there is a token that is black on one side and white on the other. Initially all tokens are placed with the white side facing up. On each move three tokens in ...
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### Miss Toad and her frogs

Miss Toad owns a lot of frogs. These frogs are all looking the same, but they can be either mad or nicely. If a mad frog is in a room with 3 nicely frogs, then he turns red, because he is ashamed. ...
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### Help me solve this question from a culture fair IQ test?

Cannot wrap my head around these 2, please also tell me what the logic is? For the 2nd one I think it might be a water droplet shape? But not sure about the logic. Thank you
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During their holidays Martina, Karl and Jim played badminton every day. The winner of each match continues to play in the next match against the one who just had a break, while the loser of this ...
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### What am I to A? | Riddle

If teresa's daughter is my daughter's mother, what am I to teresa? Grandmother Mother Granddaughter I am teresa
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### How many codes are possible?

The line - codes we are looking at consist of black and red lines. These lines can have width 1 or 2. Black and red lines are taking turns, black line, red line, black line, ... The code ends and ...
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### Resolve these Highly Narcissistic Relations

$U$, $V$, $C$ , $D$ , $E$, $F$, $G$, $H$, are distinct digits, varying from 1 to 9. $UVCD$, $EFGHD$, $EHHEV$ are concatenated numbers. Please deduce these with concise reasoning from the given ...
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### Take out one Third..Keep Two Third..To Total Ten

There are total 36 numbers in the grid shown in the picture. Cross out 12 of them and keep 24 of them. Sum of the rest of the numbers should total 10 for each row and column.
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### Help the IT guy heal one of his hard drives [duplicate]

There are $64$ hard drives each with one extra bit ("flag"), the value of which you don't know (it can be '$0$' or '$1$'). One hard drive is infected with virus that you need to heal. You have two ...
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### Give these Digits their own Place..Place them Right

In their own Circle. Such that the arrows point to successive numbers . Start with 1 and end with 9. There might be more arrows than necessary. Find the solution with least number of arrows ignored.
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### It is not as Simple as it Looks to get the right Alignment

Of these US Coins (Quarter and Dime Combo). Initial arrangement of the coins as shown in the picture is as follows... Q D Q D Q D Q Objective is to attain the final configuration... Q Q Q Q D D D. ...
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### 5 cars in a roundabout traffic

Five cars are driving in a roundabout traffic at the same moment. Each comes from an other direction, and drives less than one full round. Also each car leave the roundabout traffic in an other ...
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### Numbers 1 to 10 in the circles

The objective is to enter the numbers 1,2,3,4,5,6,7,8,9,10 in the blue circles. Doing this, the sum of the numbers has to be equal in the three connected rectangles (a rectangle consists of 4 ...
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### Go Get the Six Six-Pack

And fill with right Mathematical operands and enjoy. Six Relations shown in the pictures are missing the right operands. You can only use plus, minus, multiplication, division signs in between the ...
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### 3 guys play frisbee [on hold]

Story: Three guys A, B and C meet daily to play frisbee. They determined: Always if A doesn't have a frisbee, then B has one. If B doesn't take along a frisbee, then C has one. Today B hasn't ...
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### A Prime Length Rope into Prime length ropes

We have a rope with a prime unit length, and we need to divide this rope into $9$ ropes by cutting it with prime and/or 1 unit lengths. After cutting the rope, you are supposed to find any kind of ...
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### Deduce the Missing Digits from the given Relations

Picture shown below contains 3 horizontal and 3 vertical relations. Digits to be filled vary from 1 to 9. Order of operations is given following the arrows vertically and horizontally.
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### Be Quick and Calculating..Take Four Shots

To Target Sum of 100 Exactly . By shooting the right different numbers in four shots summing upto 100.
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### Red and Blue Dividing Line

In the grid shown below, 20 numbers are given in blue and red. Draw a dividing line along the contours of the grid such that A) Blue Numbers Sum to the same on both sides of the line B) Red Numbers ...
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### Mystic Island Math - Can you Figure it out?

On Mystic Island math is done via symbols. Distinct symbols represent distinct digits, varying from 0 to 9. From the picture below, figure out the corresponding digits. Please provide your reasoning....
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### How do you Solve an Age-Old Problem? [closed]

Mansion has a son (Mark) and a daughter (Mindy). Mark is older than Mindy. Five years ago, Sum of Mark and Mindy’s ages was twenty two. Five years from now, Mark will be exactly twice as old as Mindy....
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### Jack and Jill went up the Hill to play

A Simple Card Game. This deck of cards has only four cards simply labeled 1, 2, 3, 4. They are placed face down. Jack and Jill take turns to draw a card. You sum up the numbers drawn so far after ...
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### Riddle to Code 2: The return of numbers

The first is a pirates favorite letter. The second is from a famous quote of shakespear. The third is squaring it off in a famous formula. The fourth is the first in a very well known song. ...
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### Express 50 to 100 with constituent digits only…my 100th pzl on 50th day

Using the following rules only, Express the numbers from 50 to 100 using only digits in the number. Concise with minimum number of characters is preferred. No concatenation of numbers allowed. Only, ...
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### Find the “X “in the Box

Interlocked Rings shown in the picture share a common sum of 28. The numbers to be filled vary from 1 to 12 and do not repeat. Already four numbers..8, 9, 10, 11 are placed. Fill the X s with rest ...
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### Too early in the morning to have SODA?

Each letter shown represent distinct digit...can vary from zero to nine. $COCA$, $COLA$, $SODA$ are three concatenated numbers. Figure these out from the following relation: $COCA + COLA = SODA$
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### Can you open the door or die? v2

This is the follow up question to my previous question You wake up and find yourself in a very strange room with a single door. You find a note on the ground surrounded by lots of cards: ...
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### All the Signs point to the Second Prime…Figure out the Missing Digits

$Given$ The six Interrelated Equations A, B, C, D, E, F All equal to 3. Allowed Digits.. 1 to 9. All the missing 9 are distinct...9?s...9 Different Digits Fillin all the digits that satisfy all ...
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### 16 people, make 3 consecutive round of 4 players

I am struggling with this issue for a tournament I am planning. Take 16 people. Consider a 4-player game. To be clear, in each round all 16 players must play the game once. I want to make at least 3 ...
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### Can you open the door or die?

You wake up and find yourself in a very strange room with a single door. You find a note on the ground surrounded by lots of cards: There are 66 green and 66 blue door cards on the ground. If you ...
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### I am caught when I was about to steal some candies

I am a eight years old boy, I love candies, but my mom does not want me to eat any more candies because I start to have black teeth :( but I still love candies so... Today when I was about to steal ...
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### Is it True that Two + Two = 2? If so, what is Ten + Ten and Nine + Nine?

Given: SIX + ZERO = 4 TWO + THREE = 15 FIVE + SIX = 88 ONE + TWO = 83 TEN + TWO = 13 If so, is TWO + TWO = 2 correct? What is TEN + TEN ? NINE + NINE ? Hint 1
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### The Harry Potter Potions Riddle

A simple riddle from the first Harry Potter book. You are in a room with seven potions. There is a doorway ahead and a doorway behind, both engulfed in flames. Which potion will allow you to move ...
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### Please figure out this Pan digital Prince

Given: P, R, I, N, C, E, T, O, M are all distinct digits varying from 1 to 9. PCRON, PRINCETOM are two concatenated numbers. PCRON is the highest possible number you can have fulfilling the ...
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### Make 2019 Factorial Multiplication a perfect square

N is not a square number and consists of 2019 factorial multiplication as shown below: $N=1!\times 2!\times 3!\cdots 2018!\times2019!$ At least how many factorial needed to be removed from the ...
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### Next date with distinct digits

The date today is 7th June 2019, or 07/06/2019 (using the English DD/MM/YYYY ordering). When is the next date that when written in this way has all eight digits different?
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### Masyu puzzles with many circles

The rules of Masyu: Make a single loop with lines passing through the centers of cells, horizontally or vertically. The loop never crosses itself, branches off, or goes through the same cell ...
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### Don’t let this daunting equation dissuade you to deduce the desired result

Given: A, B, P are distinct digits. AA, AAA, ABB are concatenated numbers. Relations: $$P=A+A+B$$ $$(AA + ABB)^P-(ABB)^P=(AAA - A) ^P+(B+B^B*B)^P+(B^B)^P$$ Don’t be afraid to make reasonable ...
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### Six liars, truth-tellers and jokers

As in this puzzle, there are three different kinds of people: truth-tellers (always telling the truth), liars (always lying) and jokers (who may either tell the truth or lie). Based on these aspects ...
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### $1$ of $100$ Homes

On Crossfield Housing Estate, there are exactly $100$ homes numbered from $1$ to $100$. Rook is living in one of them. Kaito hasn't met with him for a long time and wants to pay a visit. Here is some ...
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### Winning Strategy for the Magician and his Apprentice

There are $13$ upside-down opaque cups and $2$ balls, a magician and his apprentice and yourself. You decide under which cups to put the balls, and the objective of the magician is to find the two ...
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### A $3\times3$ ColorSaw

The pieces of this ColorSaw have been flipped, rotated and moved. Can you reassemble the puzzle so that each adjacent side has the same color/shape?
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### A $2\times2$ ColorSaw

The pieces of this ColorSaw have been flipped, rotated and moved. Can you reassemble the puzzle so that each adjacent side has the same color/shape? Please explain your logic!
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### The Guys - Logic #1 - Comics

Welcome to the first in a series of quick logic puzzles. The stories behind the puzzles follow 3 guys who are life long friends, went to school together, and now work in the IT field together in Tampa....
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### The Guys - Logic #2 : Ways to work

So the guys are back. This time, they decide to change up their way to work. Let's see what they're up to... Start the two minute timer... 1. Since Anthony and Charles weren't taking the bus today, ...
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### The Guys - Logic #3 - The Casino

Oh boy, the guys went to the casino.. Let's see what these three are up to tonight. I wonder if going to the casino was a good idea?? Maybe for a couple of them. Start the two minute timer... The ...