How can you write nineteen in a manner that if we take out one, it becomes twenty?

Do You See It?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

In the image given, you can find several triangles. Can you count them all?

Begin with a word, five letters to my name,
Remove the first and last but I am the same
Take out my middle and still, I remain.
What word am I?

Use the numbers 2, 3, 4 and 5 and the symbols + and = to make a true equation. Conditions: Each must be used exactly once and no other numbers or symbols can be used.

what's the probability of getting a king or a queen from a pack of 52 cards?

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?

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

A woman lives in a skyscraper thirty-six floors high and is served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?