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 Traffic Light Riddle
There is a traffic light at the top of a hill. Cars can't see the light until they are 200 feet from the light.
The cycle of the traffic light is 30 seconds green, 5 seconds yellow and 20 seconds red.
A car is traveling 45 miles per hour up the hill.
What is the probability that the light will be yellow when the driver first crests the hill and that if the driver continues through the intersection at her present speed that she will run a red light?
The cycle of the traffic light is 30 seconds green, 5 seconds yellow and 20 seconds red.
A car is traveling 45 miles per hour up the hill.
What is the probability that the light will be yellow when the driver first crests the hill and that if the driver continues through the intersection at her present speed that she will run a red light?
Hint:
The probability of the driver encountering a yellow light and the light turning red before the car enters the intersection is about 5.5%.
At 45 mph the car is traveling at 66 feet/second and will take just over 3 seconds (3.03) to travel the 200 feet to the intersection. Any yellow light that is in the last 3.03 seconds of the light will cause the driver to run a red light.
The entire cycle of the light is 55 seconds. 3.03/55 = 5.5%. Did you answer this riddle correctly?
YES NO
At 45 mph the car is traveling at 66 feet/second and will take just over 3 seconds (3.03) to travel the 200 feet to the intersection. Any yellow light that is in the last 3.03 seconds of the light will cause the driver to run a red light.
The entire cycle of the light is 55 seconds. 3.03/55 = 5.5%. Did you answer this riddle correctly?
YES NO
Safe And Secure Riddle
As a whole, I am both safe and secure.
Behead me, and I become a place of meeting.
Behead me again, and I am the partner of ready.
Restore me, and I become the domain of beasts.
What am I?
Behead me, and I become a place of meeting.
Behead me again, and I am the partner of ready.
Restore me, and I become the domain of beasts.
What am I?
Hint:
An Electric Train Riddle
An electric train is moving north at 100mph and a wind is blowing to the west at 10mph. Which way does the smoke blow?
Hint:
Ticking In Its Weary Pace
Time is writ upon my face
My heart ticks in its weary pace.
Though wind and rain do leave their trace,
I watch them in their endless race.
What kind of clock is it, though?
My heart ticks in its weary pace.
Though wind and rain do leave their trace,
I watch them in their endless race.
What kind of clock is it, though?
Hint:
Taking You To School
This vehicle makes frequent stops
So getting to places can be slow
In London theyre usually red
The ones you take to school are yellow
So getting to places can be slow
In London theyre usually red
The ones you take to school are yellow
Hint:
The Last Burger
Hint:
Strings Never Win
Hint:
Lights On A String
Adding some lights on a string
And later underneath me
They place the gifts that they bring.
I am a...
Hint:
The Fourth Column Riddle
Do you know which one of the given options will take place of the fourth column?
Hint:
The correct choice will be the option 'd'.
In each succeeding row, the previous column is reversed and the lowest digits are omitted. Did you answer this riddle correctly?
YES NO
In each succeeding row, the previous column is reversed and the lowest digits are omitted. Did you answer this riddle correctly?
YES NO
A Blind Man Has 2 Red Pills And 2 Blue Pills Riddle
Hint:
Break each of the pills in half, as you do this pop one half in your mouth and lay the other half aside for tomorrow. When he’s done this with all four pills he will have consumed one red pill and one blue pill. And have the same left over. Did you answer this riddle correctly?
YES NO
YES NO
Hunter Polar Bear Riddle
He sees a bear and is about to shoot it.
The bear grabs his gun and eats it.
The hunter runs away one mile east.
He then walks one mile north and gets back to his camp and changes his underwear.
What color was the bear?
Hint:
He starts at at the NORTH POLE.
This means he walks south for a mile, but when he heads east for a mile he's just walking round in part of a circle, and stays one mile from the North pole. Therefore he only has to walk a mile north to get back!
So what color is the bear? It has to be a polar bear, so it's WHITE! Did you answer this riddle correctly?
YES NO
This means he walks south for a mile, but when he heads east for a mile he's just walking round in part of a circle, and stays one mile from the North pole. Therefore he only has to walk a mile north to get back!
So what color is the bear? It has to be a polar bear, so it's WHITE! Did you answer this riddle correctly?
YES NO
A Blind Man Named Grandpa Riddle
Why did Grandpa commit suicide despite his eye operation was successful?
Hint:
When blind man "Grandpa" opened his bandages, the train must be passing through the dark tunnel. The man thought he was still blind and hence commit suicide. Did you answer this riddle correctly?
YES NO
YES NO
A Prisoner Escaped From A Prison Riddle
Hint:
The man was more than halfway across a bridge when he spotted the police car, so the quickest way to leave the bridge was to run towards the police car and then turn and run into the woods to hide. Did you answer this riddle correctly?
YES NO
YES NO
A Woman Was In Court For Killing Her Husband Riddle
The entire jury stares at the doors waiting for waiting for this woman's husband to walk through the doors. The lawyer and the woman stare at the jury.
The lawyer concludes by saying, "See! If you were so sure she killed her husband, you wouldn't be watching that door!"
The jury immediately gave a guilty verdict. Why?
Hint:
The woman was watching the jury and not the doors because she knew that her husband wouldn't walk through them because she had killed him. If she has really missed him like she said, she would have been watching the doors. Did you answer this riddle correctly?
YES NO
YES NO
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