Can you make four (4) nines (9) equal 100?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

Solve the puzzle by telling what does below picture means.

How can a man go eight days without sleep?

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

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

You’ll find me on Mercury, Earth, Mars, Jupiter, Saturn, and Uranus. But never Neptune, or Venus. What am I?

You can see three almost identical images below. Can you spot the odd one out from them?

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle: