When 99 is considered higher than 100?

What is the last thing you take off before bed?

If an electric train is travelling south, then which way is the smoke going?

John and his wife were living in a rural place. On a particular day, John's wife fell ill and he called the local doctor. When the doctor picked up, he said, "Doctor, my wife is ill. She might have appendicitis."

"This can't be possible! I took out her appendix two years ago myself," the doctor explained.

When diagnosed, John's wife was found to have appendicitis. How can this be possible?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Imagine you are in a room with no windows or doors. How will you get out?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

The dirtier I get, the whiter I look. Who am I?