I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

You are stuck on an island where you have nothing. You find four pieces of paper somewhere on the island. What will be your strategy to escape from the island safely?

PS: No other resource is available to you on the island, neither can you build anything.

John and Jenni are a married couple. They have two kids, one of them is a girl. Assume safely that the probability of each gender is 1/2.
What is the probability that the other kid is also a girl?

Hint: It is not 1/2 as you would first think.

I look at you, you look at me I raise my right, you raise your left. What am I?

Using Only Five 5's and any mathematical operator make sum as 37

Solve this tricky question. You are trapped in a forest. With you, you have a gun preloaded with two bullets in it. In front of you, there is a tiger, a leopard and a jaguar.

How do you survive?

How many sides does a circle have?

81 x 9 = 801. What must you do to make the this equation true?

The more you take me, the more you leave me behind.
Who Am I?