Questions tagged [probability]

A mathematical puzzle whose essential nature involves randomness.

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votes
2answers
667 views

Open doors brain teaser [closed]

There are three doors before you, of which only one is correct. Each door will take you one minute to open by default, but one of the incorrect doors contains a trap that will slow opening of any ...
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2answers
1k views

question involving two deck of cards [closed]

Consider two identical card packs: A and B. One card is taken from A and shuffled with pack B. The top card of pack A is QUEEN of HEARTS. What is the probability that the top card of pack B is KING of ...
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2answers
174 views

Witches' Coffee [closed]

Two witches make a nightly visit to an all-night coffee shop. Each arrives at a random time between 0:00 and 1:00. Each one of them stays for exactly 30 minutes. On any one given night, what is the ...
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2answers
226 views

Darts on a dartboard [closed]

I have $x$ darts that I randomly throw on a dartboard with $y$ slots (the v shaped slices like you get when you cut a cake). Now I select a particular slice on the dartboard . What's the probability ...
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votes
3answers
395 views

This Dice Blackjack game - is there Nash equilibrium?

This dice Blackjack is game for two - bettor and dealer. It is played with fair six-sided dice. Bettor: Bettor starts the game. Bettor can roll dice as many times he/she desires while the sum of ...
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1answer
76 views

Place Your Bets 3 , last of the series

A harder sequence to figure out... What are the next 4 cards, including suits?
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2answers
136 views

Solitaire wins and losses

Let say a solitaire game can be solved 1 in 10 plays. (A play is defined as shuffling of cards and trying to solve the solitaire). If after each successfully solved game we skip 8 games (we ...
0
votes
1answer
81 views

Taking a ball from basket challenge [duplicate]

I have 10 red balls, 10 blue balls, and 2 baskets. You are free to choose the numbers of red balls, and the numbers of blue balls to put to the first basket. Then you have to put rest of the balls to ...
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votes
1answer
997 views

100 coins (Heads and Tails) [duplicate]

"You have a 100 coins laying flat on a table, each with a head side and a tail side. 10 of them are heads up, 90 are tails up. You can't feel, see or in any other way find out which side is up. ...
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votes
0answers
122 views

duel of 3 people shooting [duplicate]

$3$ people $A,B,C$ are shooting each other. The chance that $A$ will hit in a single shot is $0.2$, The chance for $B$ to hit is $0.3$ and for $C$ is $0.1$. If one hit a person, he will continue to ...
-1
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4answers
1k views

Do you choose the other door? [duplicate]

You are on the final round of a TV gameshow, there are 3 doors; A, B and C. Two doors lead to a goat and the other door leads to a sports car. In each episode the presenter asks the contestant to ...
-1
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2answers
171 views

A chance to know 52 cards [closed]

This is the Follow up Question to A game with 52 cards. So it requires to understand previous question! I believe it is a bit harder to find! what is the chance to know the positions of all the face-...
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2answers
275 views

Kill for a young body [closed]

FROM 2013 Real Playing Game. Here's the trailer. You are an old, deathly-ill multimillionaire. A biotech company has developed some brain transfer technology and offers you the chance to ...
-2
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7answers
3k views

Multiple Choice Puzzle

What are the chances of getting this correct if you pick at random? 1/4 1/2 1/3 1/4 You are not allowed to add more answers to this list Note; This DOES have a correct, demonstrable answer!
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votes
2answers
202 views

It rains in Gadyukino

It rains in Gadyukino village every other day on average. Assume the probability of rain on any given day is 50% and independent. A local weather forecaster has the sole duty every day of predicting ...
-2
votes
1answer
301 views

The Programmers Bot!

Dr. Probot is a famous inventor, known for many creations, his most recent being "Bot". Bot is the very first working robot, he has 3 very basic instructions: Left Right Self Destruct Left: Rotate ...
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votes
3answers
481 views

The 3 Boxes Show! [duplicate]

A variation of the Monty Hall, where the values inside the choices are changed You were just out gambling and lost 5000 dollars! Of course being the gambler that you are, you pay 2500 to play this ...
-3
votes
5answers
230 views

Interesting card combinations [closed]

In a normal pack of playing cards (without jokers), the probabilities of the following events are the same: (1) Drawing a set of 4 different cards (irrespective of its color and suit) - let us call ...
-3
votes
9answers
616 views

5 guards, 5 doors, and probability

1st Guard: Always lies all the time. 2nd Guard: Always tells the truth all the time. 3rd Guard: 75% probability of telling the truth. 4th Guard: 50% probability of telling the truth. 5th Guard: 25%...
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votes
2answers
147 views

Chef wants to play [closed]

You are very hungry and decide to visit a restaurant with a couple of friends. You want to order three dishes for the three of you. But, the chef serves you only if the total cost of the dishes ...
-3
votes
1answer
98 views

max possible number of dice throw [closed]

Scott repeatedly rolls a pair of standard six-sided dice and keeps track of the sum of the two numbers rolled each time. So far he has not rolled any sum twice. What is the maximum possible number of ...
-4
votes
2answers
246 views

Random chord to a circle around a triangle

This puzzle is literally a math textbook question. Its only redeeming feature is that it also happens to be too broad in a surprisingly interesting way. The problem Given the circle $\mathbf O$ ...
-4
votes
1answer
198 views

A taxi was involved in a hit-and-run accident last night [closed]

A taxi was involved in a hit-and-run accident at night. Two taxi companies, the green and the blue, operate in the city. 85% percent of the taxis are green and 15% are blue. A witness identified the ...
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votes
3answers
118 views

What is the probability that no one will get his envelope? [closed]

You are given 100 addressed envelopes and 100 addressed letters to be inserted into the envelopes. If the letters are inserted randomly into the envelopes, what is the probability that no letter will ...
-4
votes
1answer
175 views

Bad mouse, good mouse [closed]

In a certain city, there are only two companies (called Company A and Company B), that manufacture computer mice. The computer mice from Company A last $x$ hours before needing to be recharged, ...
-5
votes
2answers
289 views

The four prisoners [closed]

Four prisoners, 1, 2, 3 and 4, are all condemned to death. One of them is at random selected to be pardoned. 1 asks the guard who will be executed. The guard refuses to tell him so instead 1 says '...
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votes
1answer
210 views

Black socks and green socks [closed]

Some green socks, some black socks, their total is four. Some green socks, some black socks, some socks on the floor. The chance of getting two black ones, the chance of getting two black ones, that ...
-6
votes
5answers
140 views

Underpants in a Drawer [closed]

I have 22 underpants in the drawer and it is dark and I cannot identify the colors. 3 pairs are red. What is the probability of my putting on a red pair of underpants from the drawer? 3/22 is the ...
-6
votes
1answer
560 views

Trick-Or-Treat Probability Puzzle [closed]

On Halloween night, a young boy was trick-or-treating. It was late at night and he was on his last stop. He knocked at the door and said: Trick-or-Treat! The man inside said he had a bag of just 4 ...
-6
votes
1answer
261 views

The Puzzling Phone [closed]

The amazing "Puzzling Phone", comes in two models, one sold by "Super Puzzling Inc", and one sold by "Mega Puzzling Ltd" Phones need to have government testing before they can be sold on the market. ...
-9
votes
1answer
1k views

Coins, Dice, and Probability! [closed]

Background: It's time for a little bit of fun, your friends are playing a game and you decide to join them! Gamplay: You each sit down and play on a flat surface. You sit in a circle and each throw ...