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

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

Guess the hidden movie name?

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

Why Aeroplane windows are round?

Find the missing value of "?" in the letter sequence below.

CAD
EBG
KBM
OCR
DDH
NL?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

People make me, save me, change me, raise me. What am I?