I travel all around the world but always stay in the corner. What am I?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

I ask Joseph to pick any 5 cards out of a deck with no Jokers.

He can inspect then shuffle the deck before picking any five cards. He picks out 5 cards then hands them to me (Jack can't see any of this). I look at the cards and I pick 1 card out and give it back to Joseph. I then arrange the other four cards in a special way, and give those 4 cards all face down, and in a neat pile, to Jack.

Jack looks at the 4 cards i gave him, and says out loud which card Joseph is holding (suit and number). How?

The solution uses pure logic, not sleight of hand. All Jack needs to know is the order of the cards and what is on their face, nothing more.

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.