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Archive for November, 2010

1000 coin flip

Posted by Chris under Logic (22 Responds)

1000 fair (and normal H/T) coins are flipped. At least 999 of them landed showing heads.
What is the probabiity that the other coin is a heads?
What is the probability of throwing at least 999 heads?

Heads or Tails? (yet again)

Posted by Chris under Logic, Tom (43 Responds)

A classic that I haven’t see for ages (it’s this or nothing).
You have two coins.  One is a normal head/tail coin, the other has two heads.  They are placed in a box and shaken.  You pull one out of the box and place it on a table – without looking at it.  You then look [...]

Insert missing letter

Posted by nordtorp under wordfun (24 Responds)

Find which letter should replace the question mark.
     J P T
  E M R X Y
A I V B F B E
  C Q M G I
     X T ?

Feet on the bus

Posted by nordtorp under MathsChallenge (34 Responds)

There are seven girls in the bus. Each girl has seven bags, with seven cats. Each cat has seven kittens.
How many feet are in the bus?

Out of order

Posted by Chris under Logic, Tom (37 Responds)

A drink machine has three options Coke, Pepsi and Random (i.e. Pepsi or Coke).  Each drink is $1.  A friend tells you that the machine is faulty and that all the buttons are incorrect.
How much money would you need to spend to know which buttons deliver which drinks?

Fag problem

Posted by Chris under Logic (17 Responds)

Mr. Striker is walking home across the park.  It is a walk which takes exactly two cigarettes.  In his cigarette case he has two Craven Doodahs and a pair of El-Rashids(which he prefers).
What are the chances of his smoking two El-Rashids in such a walk if he randomly withdraws cigarettes from the case.

Ain’t that the truth!

Posted by Chris under Logic (45 Responds)

Which of the following statements are true and which are false?
1. At least one of these ten statements is false.
2. At least two of these ten statements are false.
3. At least three of these ten statements are false.
4. At least four of these ten statements are false.
5. At least five of these ten statements are [...]

Clean Shaven

Posted by Spencer under Logic (12 Responds)

In a village, the barber shaves everyone who does not shave himself/herself, but no one else.
Who shaves the barber?

A flipping fortune

Posted by Chris under MathsChallenge (32 Responds)

Starting with $1, you begin flipping a coin. Each time it comes up heads you double your money.  You stop when the coin lands tails up, but you keep all the money.  On average, how much money do you expect to have after one game.  I’ve no idea where the money is coming from.
Example.  You flip HHT, [...]

Seating arrangements

Posted by Chris under MathsChallenge, Tom (24 Responds)

Thirteen friends decide to go to the movies.  In the theater there are rows of 13 seats.  For some stupid reason they decide that the first person to enter the row may sit wherever he chooses.  The second person must sit on either side of him with no empty seat between.  The third person may sit [...]

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