100 Blank Cards Riddle
Someone offers you the following deal:
There is a deck of 100 initially blank cards. The dealer is allowed to write ANY positive integer, one per card, leaving none blank. You are then asked to turn over as many cards as you wish. If the last card you turn over is the highest in the deck, you win; otherwise, you lose.
Winning grants you $50, and losing costs you only the $10 you paid to play.
Would you accept this challenge?
There is a deck of 100 initially blank cards. The dealer is allowed to write ANY positive integer, one per card, leaving none blank. You are then asked to turn over as many cards as you wish. If the last card you turn over is the highest in the deck, you win; otherwise, you lose.
Winning grants you $50, and losing costs you only the $10 you paid to play.
Would you accept this challenge?
Hint: Perhaps thinking in terms of one deck is the wrong approach.
Yes!
A sample strategy:
Divide the deck in half and turn over all lower 50 cards, setting aside the highest number you find. Then turn over the other 50 cards, one by one, until you reach a number that is higher than the card you set aside: this is your chosen "high card."
Now, there is a 50% chance that the highest card is contained in the top 50 cards (it is or it isn't), and a 50% chance that the second-highest card is contained in the lower 50. Combining the probabilities, you have a 25% chance of constructing the above situation (in which you win every time).
This means that you'll lose three out of four games, but for every four games played, you pay $40 while you win one game and $50. Your net profit every four games is $10.
Obviously, you have to have at least $40 to start in order to apply this strategy effectively. Did you answer this riddle correctly?
YES NO
A sample strategy:
Divide the deck in half and turn over all lower 50 cards, setting aside the highest number you find. Then turn over the other 50 cards, one by one, until you reach a number that is higher than the card you set aside: this is your chosen "high card."
Now, there is a 50% chance that the highest card is contained in the top 50 cards (it is or it isn't), and a 50% chance that the second-highest card is contained in the lower 50. Combining the probabilities, you have a 25% chance of constructing the above situation (in which you win every time).
This means that you'll lose three out of four games, but for every four games played, you pay $40 while you win one game and $50. Your net profit every four games is $10.
Obviously, you have to have at least $40 to start in order to apply this strategy effectively. Did you answer this riddle correctly?
YES NO
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In a new hotel containing 100 rooms, Tom was hired to paint the numbers from 1-100 on the doors. How many times will Tom have to paint the number 8?
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The answer is 20. Many people have been guessing anywhere from 9 to 19, but the correct answer is 20. Did you answer this riddle correctly?
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You're standing in front of 2 identical doors.
One leads to heaven, one leads to hell.
There is an angel and a devil.
They are identical, but the angel always tells the truth, the devil always lies.
How do you find out which door leads to heaven?
One leads to heaven, one leads to hell.
There is an angel and a devil.
They are identical, but the angel always tells the truth, the devil always lies.
How do you find out which door leads to heaven?
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Ask either one of them which door "THE OTHER ONE" would tell you was heaven... and that's the hell door. Did you answer this riddle correctly?
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A man is wearing all black. Black shoes, socks, trousers, jumper, and gloves. He is walking down a black street with all the street lamps off. A black car is coming towards him with its lights off but somehow manages to stop in time.
How did the driver see the man?
How did the driver see the man?
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