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?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

Find the number of squares in the below picture

Spot 5 differences in two Christmas tree below:

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

What can jump higher than a building?

You bought me for dinner but never eat me. What am I?