What is the fastest way to double your money?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

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

Do you know what I am?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

A professor thinks of two consecutive numbers between 1 and 10.
'A' knows the 1st number and 'B' knows the second number

A: I do not know your number.
B: Nor do I know your number.
A: Now I know.

What are the four solutions for this?

What does it mean?

The measurement of time, That can't be found on a clock, But can be looked upon on a map.

Who is He ?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.