Which number should replace the question mark?

Can You Find the Missing Zero? A Number Puzzle that Will Trick Your Eyes

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

Can you identify the hidden rebus in the image below?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different. How do you measure 45 minutes?

What came first, the chicken or the egg?

A game is being played where eight players can last for thirty-five minutes. Six substitutes alternate with each player in this game. Thus, all players are on the pitch for the same amount of time including the substitutes.

For how long is each player on the pitch?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

Highly detail-oriented individuals excel at this type of optical illusion challenge. It requires not just good eyesight but also the ability to distinguish subtle differences quickly. Finding the 6 among all these 9's could indicate a high level of IQ and superior observational skills.

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?