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
The Prime Number Riddle
Two hundred people in an auditorium are asked to think of a single digit number from 1 to 9 inclusive and write it down. All those who wrote down a prime number are now asked to leave. Ninety people remain behind in the hall. How many of these are expected to have written down an odd number?
Hint: Remember that 1 is not a prime number.
Those that remain behind must have written {1,4,6,8,9} and from this only {1,9} are odd. The probability of an odd number is thus 2/5.
Expected number of odds is 2/5 * 90 = 36 Did you answer this riddle correctly?
YES NO
Expected number of odds is 2/5 * 90 = 36 Did you answer this riddle correctly?
YES NO
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:
An Absentminded Philosopher Riddle
An absentminded philosopher forgot to wind up the only clock in his house. He had no radio, television, telephone, internet, or any other means of ascertaining the time. He therefore decided to travel by foot to his friend's house, a few miles down a straight desert road. He stayed there for the night and when he came back home the following morning, he was able to set his clock to the correct time. Assuming the philosopher always walks at the same speed, how did he know the exact time upon his return? Note: this is not a trick question. The Philosopher did not bring anything to his friend's house, nor did he bring anything back with him on his trip home.
Hint: We can assume that the journey to his friend's and back took exactly the same amount of time.
He Philosopher winds the grandfather clock to a random time right before leaving, 9:00 for example. Although this is not the right time, the clock can now be used to measure elapsed time. As soon as he arrives at his friend's house, the Philosopher looks at the time on his friend's clock. Let's say the time is 7:15. He stays overnight and then, before leaving in the morning, he looks at the clock one more time. Let's say the time is now 10:15 (15 hours later). When the Philosopher arrives home, he looks at his grandfather clock. Let's say his clock reads 12:40. By subtracting the time he set it to when he left (9:00) from the current time (12:40) he knows that he has been gone for 15 hours and 40 minutes. He knows that he spent 15 hours at his friends house, so that means he spent 40 minutes walking. Since he walked at the same speed both ways, it took him 20 minutes to walk from his friend's home back to his place. So the correct time to set the clock to in this example would therefore be 10:15 (the time he left his friend's house) + 20 minutes (the time it took him to walk home) = 10:35. Did you answer this riddle correctly?
YES NO
YES NO
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:
Tree Embroidery Riddle
Hint:
Naughty Eyeball Riddle
Hint:
Between An Elephant's Toes Riddle
Hint:
Five Potatoes Riddle
A mother has six children and five potatoes. How can she feed each an equal amount of potatoes? Do not use fractions.
Hint:
Thousands Of Letters Riddle
Hint:
1 Rabbit Saw 6 Elephants Riddle
1 rabbit saw 6 elephants while going to the river.
Every elephant saw 2 monkeys going towards the river.
Every monkey holds 1 parrot in their hands.
How many Animals are going towards the river?
Every elephant saw 2 monkeys going towards the river.
Every monkey holds 1 parrot in their hands.
How many Animals are going towards the river?
Hint:
5 Animals.
Lets go through the question again.
1 rabbit saw 6 elephants while going to the river. Hence, 1 animal (rabbit) is going towards the river.
Every elephant saw 2 monkeys going towards the river. This is the tricky part, from the sentence it seems to imply each of the 6 elephants saw 2 monkeys going towards the river, hence logically will be 6 x 2 = 12 animals (monkeys) going towards the river.
However, the statement does not explicitly mention that Every elephant saw 2 DIFFERENT monkeys, hence implicit rules apply and infer that the 2 monkeys are the same.
Hence, correct answer is that every elephant saw 2 monkeys, and by inference, the 2 monkeys are the same, hence there exists only 2 monkeys which are going towards the river !!
Finally, every monkey holds 1 parrot in their hands. Hence, 2 parrots are going towards the river.
So in total, 1 rabbit, 2 monkeys and 2 parrots (5 animals) are going towards the river. Did you answer this riddle correctly?
YES NO
Lets go through the question again.
1 rabbit saw 6 elephants while going to the river. Hence, 1 animal (rabbit) is going towards the river.
Every elephant saw 2 monkeys going towards the river. This is the tricky part, from the sentence it seems to imply each of the 6 elephants saw 2 monkeys going towards the river, hence logically will be 6 x 2 = 12 animals (monkeys) going towards the river.
However, the statement does not explicitly mention that Every elephant saw 2 DIFFERENT monkeys, hence implicit rules apply and infer that the 2 monkeys are the same.
Hence, correct answer is that every elephant saw 2 monkeys, and by inference, the 2 monkeys are the same, hence there exists only 2 monkeys which are going towards the river !!
Finally, every monkey holds 1 parrot in their hands. Hence, 2 parrots are going towards the river.
So in total, 1 rabbit, 2 monkeys and 2 parrots (5 animals) are going towards the river. Did you answer this riddle correctly?
YES NO
Starts Off Temporary
Hint:
Princess Charming Kiss
Hint:
Participating In A Race
Hint: It's not first place.
If you answer that you are first, then you are absolutely wrong! If you overtake the second person and you take his place, you are second! Did you answer this riddle correctly?
YES NO
YES NO
A Hobbit Party Riddle
Hint:
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