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
Eight Eights
Hint:
The Broken Grandfather Clock
A grandfather has a broken grandfather clock that is off by a minute every hour (too fast). He figures out a way, while keeping it running at the same rate, to make the clock say the correct time twice a day.
How could he do this?
How could he do this?
Hint:
What Are The Coins?
Hint:
A nickel and a quarter: one of them isn't a nickel but the other one is Did you answer this riddle correctly?
YES NO
YES NO
Made Of Ten
Made of ten but two we make,
When assembled others quake,
Five apart and we are weak,
Five together havoc wreak.
What are we?
When assembled others quake,
Five apart and we are weak,
Five together havoc wreak.
What are we?
Hint:
The One Who Buys It, Never Uses It...
The one who makes it, sells it. The one who buys it, never uses it. The one that uses it never knows that hes using it. What is it?
Hint:
September October November Riddle
In October, you cut me intentionally to make me look worse.
In November, you trash me like you never knew me.
What am I?
Hint: It helps if you think about each month differently and then as a whole.
Elf Sandwich Riddle
Hint:
Gingerbread Man Riddle
Hint:
Dancing Dogs Riddle
Hint:
I Am Two-faced Riddle
Men spill their blood for me.
I have no legs but travel widely.
I make kings immortal.
I am potent when shared,
Yet greed for my power keeps me locked away.
What am I?
Hint:
Busy Busy Bee
I'm busy, as busy as can bee,
Making honey for you and me.
My bumbling cousin is very busy too,
But she won't make honey to give to you...
What kind of bee am I?
Making honey for you and me.
My bumbling cousin is very busy too,
But she won't make honey to give to you...
What kind of bee am I?
Hint:
Making Faces Riddle
When asked what he does all day, a man answered that he sits and makes faces. What does he really mean?
Hint:
Throwing A Ball Riddle
How can you throw a ball and make it stop and come back to you without it touching anything or having anything attached to it?
Hint:
Colors Pattern Riddle
Which one of the colors (not all of that color, just one part of a group) should be changed to make the pattern correct :
1) Black : Red
2) Blue : White
3) Yellow : Black
4) Red : Red
5) Black : White
6) Blue : Black
7) Yellow: Red
8) Red : Blue
9) Black : Black
10) Blue : Red
11) Yellow : White
12) Red : Black
1) Black : Red
2) Blue : White
3) Yellow : Black
4) Red : Red
5) Black : White
6) Blue : Black
7) Yellow: Red
8) Red : Blue
9) Black : Black
10) Blue : Red
11) Yellow : White
12) Red : Black
Hint:
The latter part of # 8 should be white. The pattern on the left goes black, blue, yellow, red, black, etc, and the pattern on the right goes red, white, black, red, etc. Did you answer this riddle correctly?
YES NO
YES NO
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