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
Trapped With The Army
A man got trapped with the army, there were two papers, one said yes the other no. A man in the army said if you get the paper that sees no I will kill you, another man comes in the room sees I put no on both papers. How does he get out of it?
Hint:
He eats one. The man looks at the paper it sees no, so he thought the one the guy ate was yes. Did you answer this riddle correctly?
YES NO
YES NO
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I can come in many colors
Like red, yellow, orange, blue or green
When you put me on paper
Your drawings or writing can be seen
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When you put me on paper
Your drawings or writing can be seen
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Although my center contains lead
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And so you need to sharpen it
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I am a?
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Add it nicely to some canvas
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Instead you add it to the walls
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Instead you add it to the walls
To make a room look really neat
Its...?
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Im sometimes pink at one end but Im not lipstick
I can come in many different colors but Im not a car
I can become blunt but Im not a knife
I contain lead but Im not metallic
Im a writing instrument but Im not a pen
I am a?
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I can become blunt but Im not a knife
I contain lead but Im not metallic
Im a writing instrument but Im not a pen
I am a?
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I sometimes come in a can but Im not food
I sometimes come in a bottle but Im not a beverage
I come in different colors but Im not a rainbow
Im sometimes used with canvas but Im not a tent
Im used with a brush but Im not toothpaste
What am I?
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I come in different colors but Im not a rainbow
Im sometimes used with canvas but Im not a tent
Im used with a brush but Im not toothpaste
What am I?
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