What is common among 11, 69, and 88?

Before Mount Everest was discovered, what was the highest mountain in the world?

What is more useful when it is broken?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

How can you tell a raw egg from a hard-boiled egg?

Cristina was born in 1888. She just had her 30th birthday today how did that happen?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

A boy was locked in a room by some robbers. All that is in the room is a piano, a calendar, and a bed. The room is locked from the outside. What does he eat, drink, and how does he escape and get out?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.