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

John said, "If yesterday was tomorrow, today would be Friday."

When did John make this statement?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

Can you identify if it's a murder or a suicide ?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?