What is both possible and impossible at the same time?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

Can you place six matchsticks in a manner that each of the matchsticks is in touch with the other five matchsticks?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.
There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.
You can, however, ask one robot one question. The problem is one robot always tells the truth, the other always lies and you don't know which is which.
What is the question you ask?

Suppose that you are trapped on the surface of a frozen lake. The surface is so smooth and ideal that there is no friction at all. You cant make any grip on the ice and no wind is blowing to help you out. You have just a mobile phone with you which has got no reception disabling you to call for help.

How will you plan your escape before you freeze to death on the frozen lake?

A police officer was passing by when he saw a guy hiding. He walked up to him and genially asked, "What is your name?"

"Shut up!" the boy responded.

"Where are your manners?" asked the outraged police officer.

"Up that tree," said the boy discourteously, directing to a neighbouring tree.

You're looking for trouble, aren't you?" said the police officer.

"No, trouble is looking for me!" the boy answered solemnly.

Why is the boy behaving like this?

What has one letter and starts with an E?

Can anyone tell me a word in the English dictionary which has a silent 'z'?

Prove that twice of ten is the same as twice of eleven.