Which tank will fill first?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

John went to a parrot shop in Mexico, and the parrot owner told him that his parrot is so unique that he repeats everything he hears. John got excited and immediately bought the parrot. John went home and spoke many words, but the parrot does not repeat anything.
He went again to the parrot shop and complaint to the shopkeeper, but the shopkeeper never lied. Explain?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

You are driving down the road in your car on a wild, stormy night, when you pass by a bus stop and you see three people waiting for the bus

An old lady looks as if she is about to die.
An old friend who once saved your life.
The perfect partner you have been dreaming about.
Knowing that there can only be one passenger in your car, whom would you choose?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?