There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

What kind of tree can you carry in your hand?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

Count the number of triangles in the given picture.

Eight of us go fourth, not back, to protect our king from an attack. What are we?

I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?

In the image given, you can find several triangles. Can you count them all?

If 21x = 79x, what is the value of x?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?