Math Riddles

 
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Question: If you toss a coin ten times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

Answer: There's a 50 percent chance it will land heads up. The final coin toss is independent of the first ten tosses.

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By daddyslilgirl

Question: What single line can you add to the following statement to make it true?

5+5+5=550

Answer: Add a line to the first '+' to make it a 4.

545+5=550

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Question: There are 100 prisoners lining up to go to jail. Each prisoner is wearing a hat that is either black or white. The prisoners don't know their own hat color, just the hat color of those in front of them in line (the first prisoner in line can't see anyone's hat and the last prisoner can see everyone's hat except their own). Starting from the back, one of the guards asks each prisoner what color their hat is. If they are correct they get to go free but if they are wrong they go to jail.If the prisoners get to discuss a plan, how can at least 99 of them be saved?

Answer: The back prisoner will yell "black" if there is an odd number of black hats in front of him and "white" if there is an even number of black hats in front of him. The next prisoner will then count the number of black hats in front of him and if it was odd and is now even, or vice versa, then that person knows what color their hat is. The next person then knows their hat color based on what the people before them said and how many black hats are in front of them. In this way the front 99 prisoners will know their hat color and will be set free. The prisoner in the back who goes first has a 50 percent chance of being set free.

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Question: There are two ropes that both take exactly 1 hour to burn from end to end. You are unable to cut the rope. How can you burn the two ropes in a total of 45 minutes?

Answer: Start one of the ropes on fire from both ends and the other one from one end. After a half an hour one rope will be completely burnt and the other will be half burnt. At this point you light the final rope from the unlit side and it will take 15 minutes for the remaining half of the rope to burn, for a total of 45 minutes.

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Question: If you have two twins, three triplets and four quadruplets; how many people do you have?

Answer: 9. Two twins are 2 people, three triplets are 3 people, and four quadruplets are 4 people. 2 + 3 + 4 = 9.

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