A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

Two natural numbers have a sum of less than 100 and are greater than one.

John knows the product of the numbers and Jacob knows the sum of numbers.

The following conversation takes place between them:
John: 'I am not aware of those numbers.'
Jacob: 'I knew you wouldn't be. I am not aware myself.'
John: 'Now I know them!'
Jacob: 'Now I know them, too!'

What are the two numbers?

At a party, there are five people and a whole round cake lying at the centre of the table. Only four people will make a cut and take their piece and the last one will get the remaining piece on the table. How can they make sure that everyone gets a 1/5th of the piece?

Why do we preferably have round manhole covers and not square ones?

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

Can you count the number of blocks in the picture below?

How many Watermelons are there in the below picture?

What kind of band never plays music?

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?