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?

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

What is the largest number you can write with just 3 digits?

using four eights (8) and a one (1) and one mathematical symbol , create the number 100

I’m tall when I’m young, and I’m short when I’m old. What am I?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

How can you make number one disappear by adding something to it?

Look at the picture and find out which square is not linked with any of the other squares.

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

Replace the question mark with the correct number.