The Secret Santa Exchange
A group of ten friends decide to exchange gifts as secret Santas. Each person writes his or her name on a piece of paper and puts it in a hat. Then each person randomly draws a name from the hat to determine who has him as his or her secret Santa. The secret Santa then makes a gift for the person whose name he drew.
When it's time to exchange presents, each person walks over to the person he made the gift for and holds his or her left hand in his right hand.
What is the probability that the 10 friends holding hands form a single continuous circle?
When it's time to exchange presents, each person walks over to the person he made the gift for and holds his or her left hand in his right hand.
What is the probability that the 10 friends holding hands form a single continuous circle?
Hint: It's not as difficult as it seems.
It's the number of ways the friends can form a circle divided by the number of ways the names can be drawn out of the hat.
1/10
For a group of n friends, there are n! (n factorial) ways to draw the names out of the hat. Since a circle does not have a beginning and end, choose one person as the beginning and end of the circle. There are now (n-1)! ways to distribute the remaining people around the circle. Thus the probability of forming a single circle is
(n-1)! / n!
Since n! = (n-1)! * n (for n > 1), this can be rewritten as
(n-1)! / (n*(n-1)!)
Factoring out the (n-1)! from the numerator and denominator leaves
1/n
as the probability. Did you answer this riddle correctly?
YES NO
For a group of n friends, there are n! (n factorial) ways to draw the names out of the hat. Since a circle does not have a beginning and end, choose one person as the beginning and end of the circle. There are now (n-1)! ways to distribute the remaining people around the circle. Thus the probability of forming a single circle is
(n-1)! / n!
Since n! = (n-1)! * n (for n > 1), this can be rewritten as
(n-1)! / (n*(n-1)!)
Factoring out the (n-1)! from the numerator and denominator leaves
1/n
as the probability. Did you answer this riddle correctly?
YES NO
A Town With No Houses
Hint:
Exposed To A Disease Riddle
A boy and his father have been exposed to a disease. Sadly, the father rapidly develops a tumor and dies. The boy survives, but desperately needs an operation and is rushed to hospital. A surgeon is called. Upon entering the room and seeing the patient, the surgeon exclaims, Oh no! I cant do the operation. Thats my son!
Hint:
The Houses Of Parliament
This city has the river Thames
With the Houses of Parliament close by
It also has Trafalgar Square
And a Ferris wheel - The _ _ _ _ _ _ Eye
With the Houses of Parliament close by
It also has Trafalgar Square
And a Ferris wheel - The _ _ _ _ _ _ Eye
Hint:
A Metal Room With A Metal Door
A prisoner was stuck in a metal room with a metal door that was locked. There was no windows and nothing in the room but a piano. What can he do to escape?
Hint:
I Exist Where There Is Light Riddle
Hint:
Cities But No Houses Riddle
It has cities but no houses, it has oceans but no water, it has forests but no trees, it has deserts but no sand. What is it?
Hint:
Archery Experts Riddle
Hint:
A Man Is Sitting In A House At Night That Has No Lights
A man is sitting in a house at night that has no lights on at all. There is no lamp, no candle, nothing. Yet he is reading. How?
Hint:
A Mother Was Killed In A Circular House Riddle
The daughter said she was playing with her dolls, the son said he was playing outside in the garden, the maid said she was dusting corners, the butler said he was watching the son, and the chief said he was baking pies.
Who killed the mother?
Hint:
The Maid; As she said she was dusting the corners and in a round house, there are no corners... Did you answer this riddle correctly?
YES NO
YES NO
A Tiny House That You Will Find On The Shore
Hint:
Karate Expert With A Pig Riddle
Hint:
Prisoners Were Told That They Have A Chance To Be Free Riddle
The prisoners can talk to only ONE guard, and ask only ONE question. Which question should they ask to find the door that will take them to freedom?
Hint:
They should ask any guard "is the freedom door next to the lying guard?" If the guard answers "yes" they should go to the other door. if it was the liar, the other door takes them to freedom. If it was the honest guard, the other door is also what the prisoners want. If the guard answers "no" they should go to the door next to him: if it was the liar, the door next to him takes them to freedom. If it was the honest guard, the door next to him is also the right choice. Did you answer this riddle correctly?
YES NO
YES NO
A Blind Girl Lost Her Pencil Riddle
Hint:
A Zombie A Mummy And A Ghost Bought A House Riddle
Hint:
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