## Nov 21, 2009

### The Cereal Box Surprise

### Splitting Problem

## Nov 20, 2009

### An Ant and a Cube

The ant can only travel from a cube to the adjacent cubes (i.e. having common faces)

Courtesy: Nitin Basant

## Nov 18, 2009

### Monty Hall problem a.k.a. The 3 door problem

## Nov 17, 2009

### 5 Pirates Puzzle

*Stewart, Ian*

*(1999-05), "*

*A Puzzle for Pirates*

*", Scientific American: 98–99*

## Nov 15, 2009

### Information for puzzle solvers!!

**itsfreddo.toughnut@blogger.com**and have them published on this blog. I would strongly encourage all contributors to mention their names in the end of the email so that they are fairly credited for their contribution to the blog.

### The Scared Guards Problem

### 5 cards magic trick

Two magicians, John and Hull, perform a trick with a shuffled deck of cards, jokers removed. John asks a member of the audience to select five cards at random from the deck. The audience member passes the five cards to john, who examines them, and hands one back. John then arranges the remaining four cards in some way and places them face down, in a neat pile.

Hull, who has not witnessed these proceedings, then enters the room, looks at the four cards, and determines the missing fifth card, held by the audience member. How is this trick done?

Note: The only communication between John and Hull is via the arrangement of the four cards. There is no encoded speech or hand signals or ESP, no bent or marked cards, no clue in the orientation of the pile of four cards...

## Nov 14, 2009

### 6 people in a group

*x*is a friend of

*y*, then

*y*is a friend of

*x.*)

### Cocktail Party

*x*is a friend of

*y*, then

*y*is a friend of

*x.*)

**Hint:**Use pigeonhole principle

## Nov 13, 2009

### Bhaddo, Tawar and KT (Tough)

## Nov 12, 2009

### 3 Families

### Red-eyed monks and brown-eyed monks on an island?

All the monks are highly logical and devout, and they all know that each other is also highly logical and devout (and they all know that they all know that each other is highly logical and devout, and so forth).

Of the 1000 monks, it turns out that 100 of them have red eyes and 900 of them have brown eyes, although the monks are not initially aware of these statistics (each of them can of course only see 999 of the 1000 monks).

Life goes on, with brown-eyed monks and red-eyed monks living happily together in peace, and no one ever committing suicide. Then one day a tourist visits the island monastery, and not knowing that he's not supposed to talk about eyes, he states the observation "At least one of you has red eyes." Having acquired this new information, what effect, if anything does this have?

## Nov 11, 2009

### Extension of 2 eggs problem

### B'day twins problem

Sheila and He-Man are twins; Sheila is the OLDER twin. Assume they were born immediately after each other, an infinitesimally small - but nonzero - amount of time apart. During one year in the course of their lives, Sheila celebrates her birthday two days AFTER He-Man does. How is this possible?

Bonus: What is the maximum amount of time by which Sheila and He-Man can be apart in their birthday celebrations during the same year?

Note: For both Sheila and He-Man, these birthday celebrations happen on the actual birthday date -- it cannot be a celebration that occurs at a date earlier or later than the actual birthday date for whatever reasons of convenience. Also, the solution has nothing to do with the theory of relativity or any other over complicated nonsense like that.

### Globe Traversal Problem

## Nov 10, 2009

### Five selfish women, a monkey, and some coconuts (2 star)

That night each woman took a turn watching for rescue searchers while the others slept. The first watcher got bored so she decided to divide the coconuts into five equal piles. When she did this, she found she had one remaining coconut. She gave this coconut to a monkey, took one of the piles, and hid it for herself. Then she jumbled up the four other piles into one big pile again.

To cut a long story short, each of the five selfish women ended up doing exactly the same thing. They each divided the coconuts into five equal piles and had one extra coconut left over, which they gave to the monkey. They each took one of the five piles and hid those coconuts. They each came back and jumbled up the remaining four piles into one big pile.

What is the smallest number of coconuts there could have been in the original pile?

P.S. Introducing stars...according to the difficulty of problem on the scale of 1 to 5.

### Bulbs-Switches matching problem

### 25 cards in a dark room

### 2 eggs problem

* You have access to a 100-storey building.

* Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100 th floor.Both eggs are identical.

* You need to figure out the highest floor of a 100-storey building an egg can be dropped without breaking.

* Now the question is how many drops you need to make. You are allowed to break 2 eggs in the process

## Nov 9, 2009

### The Bad King Problem

A bad king has a cellar of 1000 bottles of delightful and very expensive wine. a neighbouring queen plots to kill the bad king and sends a servant to poison the wine. (un)fortunately the bad king's guards catch the servant after he has only poisoned one bottle. alas, the guards don't know which bottle but know that the poison is so strong that even if diluted 1,000,000 times it would still kill the king. furthermore, it takes one month to have an effect. the bad king decides he will get some of the prisoners in his vast dungeons to drink the wine. being a clever bad king he knows he needs to murder no more than 10 prisoners - believing he can fob off such a low death rate - and will still be able to drink the rest of the wine at his anniversary party in 5 weeks time.

explain how...

## Nov 8, 2009

### Prisoners and Hats

*N*prisoners, but there is not enough space for all of them. The jailer decides to give them a test, and if all of them succeed in answering it, he will release them, whereas if any one of them answers incorrectly, then he will kill all of them. He describes the test as follows:

I will put a hat, either white or black, on the head of each of you. You can see others' hats, but you can't see your own hat. You are given 20 minutes. I will place at least one white hat and at least one black hat. All of you should tell me the colour of the hat on your head. You can't signal to others or give a hint or anything like that. You should say only WHITE or BLACK. You can go and discuss for a while now.