Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [logical-deduction]

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

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 ...
3
votes
1answer
96 views

Horror Episode #4: Feeling Drained

A sewage worker was tasked to go down a manhole to clean up a clogged pipe. At first it didn't seem like much, just another ordinary day on the job. He went down into the manhole truly expecting ...
3
votes
2answers
143 views

Golfing match with Jim, Joanne, Ed, and Emily

Jim, Joanne, Ed, and Emily are standing on the first tee of their favorite golf course, about to begin a partners match, (A partners match pits two golfers against two other golfers). They are ...
-5
votes
2answers
160 views

Language Communication Puzzle

5 professors — A, B, C. D and E — met at a conference and were planning to discuss their Ideas with each other. Each professor speaks exactly two languages among English. French. Russian. Chinese and ...
-1
votes
3answers
239 views

Bike Riding Puzzle

Eight persons, A through H, were standing along a circular track, not necessarily in the same order, such that the distance along the track between any two persons standing adjacent to each other was ...
-5
votes
1answer
134 views

Dollars to Kids

Daam has 8 children, named Esha, Hansika, Deepa, Rinsu, Ira, Vimky, Abhiteet and Aankhal. She has 36 dollars with her. One day, she gifted the dollars among her children such that the eldest child got ...
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 ...
6
votes
2answers
234 views

The ability-swap-circle chess

This question was inspired by this question: A Battle of Dysfunctional Kings (Chess). What would be the shortest possible mate, if: Every piece moves in the same way. The way the pieces move ...
-6
votes
2answers
102 views

Fun Vacation to Maine [closed]

Some college friends decided to take a vacation in Maine together. They each had to chip in \$90 for the weeks' lodgings. They tried to convince three more people to go with them, to reduce the cost ...
-6
votes
2answers
172 views

Flowers in a circle Puzzle

Eight flowers, coded as A, B, C, D, E, F, G and H, are planted in a garden in the shape of a circle (not necessarily in that order). The flowers are of different types – Rose, Lotus, Daffodil, ...
7
votes
1answer
498 views

mobile date puzzle

A mobile company launched six mobile models — S,P,O, K, M and Z in the span of eight years. No two models were launched within a period of 18 months. The launch dates of the models are given below: <...
-1
votes
2answers
81 views

The Sneaky Sly Horse Trader [closed]

Once upon a time, there was a horse trader. One morning, the horse trader bought a horse for \$60. Just after noon, the horse trader sold the same horse back to their original owner for \$70. He then ...
-8
votes
1answer
88 views

Tennis Players Puzzle

Five tennis players of USA were asked to rank 5 football teams - P, Q, R, S and T - of other countries from 1 to 5 as per their performances in last year’s tournament, where rank 1 being the highest ...
-1
votes
1answer
104 views

Annual Meet Puzzle

The annual meet was attended by 20 persons. The persons who attended the meet have worked in eight different firms – M, BC, K, A, BA, D, PC and E. The following table provides information about the ...
6
votes
1answer
323 views

Thieves and coffee

A thief has stolen people's coffees, and switched around the prices. Can you help the store manager? These people want a refund. Try to find out which person ordered which coffee, and the ...
3
votes
2answers
317 views

yes/no logic problem

There is a truth teller (always tells the truth), a liar (always lies), and one that sometimes answers truthfully and sometimes lies. Each person knows who is who. You may ask three yes or no ...
3
votes
2answers
179 views

The Film, Student, State, and Time

Four students entered their movie in a national student film festival. Using only the clues that follow, determine for each film the director, title, running time, and state in which each was produced ...
4
votes
1answer
162 views

Salary to Employee puzzle

A Managers paid a different amount to six Employees – A, B, C, D, P and R, not necessarily in the same order. The amount paid by him to each person is not necessarily a whole number. He paid them one ...
32
votes
3answers
5k views

Mate in one with NO PIECES?

The following pictures depict chess positions one move before white checkmated black: The problem is, I seemed to have completely lost which pieces each letter/number represents. All I know is that ...
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:
0
votes
0answers
63 views

Identify the special one among 12 coins [duplicate]

We have 12 coins, and only 11 of them have the same mass. It can be assumed that all coins have identical appearances. We have a lever. How can we identify the special coin, by taking measurements ...
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 ...
0
votes
2answers
209 views

Country and Its Capital

Five Managers - K, M, N, O and P - visited five Countries, F, A, B, G and K, such that each manager visited exactly four Countries. Further, each Country has a different capital city from among Merine,...
0
votes
1answer
103 views

Finding lightest and heaviest?

Given n > 1 items and a two pan balance scale with no weights, determine the lightest and the heaviest items in $\lceil 3n/2 \rceil − 2$ weighings. I tried splitting down the middle and picking one ...
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 ...
0
votes
1answer
99 views

Home city and Visited City

P, R, S, T, U and V are six colleagues who work for Fan Inc. headquartered at USA. Each of them lives in a different city that is one out of P, R, S, T, U and V, not necessarily in that order. Their ...
5
votes
4answers
247 views

Guess the letter in one question puzzle. It's a Relic [closed]

I am thinking of one of the following five letters R E L I C You can ask me one question to guess which letter it is. Rules No question related to the number 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 ...
-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 ...
11
votes
4answers
2k views

This is simple: Just fill in the blank

Newspaper Headline Insect Researcher Carroll Appleton alongside grandson Adam discover underground wormhole networks. Recover ________ earthworms. Fill in the blank. Following are the choices ...
5
votes
1answer
181 views

Coffee and a movie with friends

The day after our wedding, me and my wife Becky met our friend Charlotte and her husband Alan for coffee and a movie. Me: Hi Charlotte! Hi Alan! Charlotte: Hi! So, are you two finally married ...
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, ...
0
votes
2answers
84 views

Cannot figure out who is saying the truth from these three statements [duplicate]

Fred: John is lying Bob: Fred is lying John: Fred is lying or Bob is lying "or" is inclusive I got that John and Bob are saying the truth while Fred is lying, but i'm not sure if it's correct (...
2
votes
2answers
173 views

Three statements, who is saying the truth?

Bob: Steve is lying Steve: Bob is lying Fred: Steve is lying or Bob is lying "or" is inclusive How would I approach this question? I honestly have no idea. I was thinking of making a truth table ...
2
votes
1answer
398 views

Missing item in pattern question

So I notice that the hexagon rises, so it should be A or B. But beyond that, I can't figure out why one of A or B would be correct and the other would not be.
8
votes
1answer
658 views

Murder in the Royal Court

An entry in Fortnightly Topic Challenge #40: Retrograde Analysis! I can't believe it! Last night we heard a bit of fighting... but we had no idea that... our King was in check, and my fellow Rook and ...
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 ...
0
votes
2answers
181 views

Screen Time Puzzle

Find the time of screening of each of the movies in each of the screens. Need help to solve this.Please share Approach. Source : IMS
-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
2answers
408 views

Water island puzzle

On a planet called T, there exists a continent called P, which is surrounded on all sides by water. The continent comprises eight countries – A, R, B, C, D, E, G and K – located contiguously on it, i....
0
votes
1answer
69 views

Athletes and their ranking

Link to Original Image Seven athletes — A1, A2, A3, A4, A5, A6, and A7 participated in a 100 m race on each day of a particular week from Sunday to Saturday. Ranks, from 1 to 7, were given to the ...
0
votes
1answer
105 views

Minesweeper challenge #4

While solving another Minesweeper puzzle, I ran into yet another unsolvable corner. Well, actually, this time I have two unsolvable corners in the same puzzle. Here's the bottom left corner: ...as ...
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 ...
2
votes
1answer
156 views

Who sits where?

Eight persons A through H each of a different profession among engineer, doctor, teacher, policeman, singer, mechanic, painter and politician are sitting in a row of eight seats facing the dias. Their ...
0
votes
1answer
104 views

Who won against Whom

Five teams from five different colleges- S, K, M, V and N, participated in Champions League (ICCL) played in the year 2008. Each team played exactly one match against every other team. But due to some ...
6
votes
1answer
142 views

Color Star (Semi - Instructionless Sum - Star)

Color Star - a semi-instructionless variation of Sum Star Known Rules of Sum Star Fill cells with numbers and shade all remaining cells such that Each dodecagon contains the numbers 1-9 exactly ...
3
votes
2answers
180 views

Who Visited and When?

During a particular year, exactly ten people ($A - J$) visited a certain city on five different days between January 1st and April 30th, in a non-leap year; such that on each of the five days, exactly ...
1
vote
1answer
188 views

Fairy Chess #2: The Angel

The sequel you've all (er, at least some of you have) been waiting for! Part 1 is here if you want to check it out. In this game, we have an entire army against a single piece yet again. This time,...