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

A man escapes from jail using help from his girlfriend. The investigators suspect four girls of being the man's girlfriend.

Out of those four girls, one is his girlfriend who is lying. Two of the girls are completely innocent and are speaking the truth. One of the girls is the man's sister who is helping the girlfriend lie. Following are the statements from all four of them:

Ariana: "Myrna is his girlfriend."
Jane: "Angelina is lying."
Angelina: "Ariana is lying."
Myrna: "Jane is not his sister."

Can you find out who is the man's sister among them?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

What does this Rebus Picture means ?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

The horse jumps over the king.
Strangely there is absolutely no scratch on him.

Can anyone explain, how is this possible?

What is the difference between a jeweller and a jailer?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

Can you find out the missing number in the grid?