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
Duck Gets Up Riddle
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How Many Ducks Do You See Riddle
Hint:
There are a total of 16 ducks in the picture. In the first row, there are 5 ducks in total. Speaking about the second row, it has 6 ducks in total. The last row has 5 ducks in total. If you see carefully there are some small ducks in the picture. It might be difficult to notice them at first glance. At first glance, you might notice around 10 ducks but there are more ducks hidden in the picture. There is also an image that will give you a clear idea of where are the hidden ducks. Did you answer this riddle correctly?
YES NO
YES NO
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A Mistletoe And A Duck Riddle
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Detective Santa Riddle
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The Turkey Crossing The Road
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Cross-eyed Teacher Riddle
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Cross The Road Riddle
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Twinkle And Rinki Cross A River
Twinkle and Rinki wish to cross a river.
The only way to get to the other side of the river is by boat, but that boat can only take one of them at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both girls manage to cross using the boat.
How?
The only way to get to the other side of the river is by boat, but that boat can only take one of them at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both girls manage to cross using the boat.
How?
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Cow Crossing The Road
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