What goes through cities and fields, but never moves?

Which number should replace the question mark?

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

John buys rice at Rs.60/kg from Britain and then sells them at Rs.5/kg in India. As a result of this, he becomes a millionaire. How come?

This was asked in an interview with Coa-Cola.

The interviewer has given me 100 marbles(50 white and 50 black) and two empty boxes.
He then told me that he will leave the room and i need to place all the marbles in two boxes.

And When he come back, he will draw a marble from any of the two box and if the marble is white I will be hired.

Also
* No box can be empty.
* All 100 marbles must be placed in one of the two boxes.

So what should I have done?

Spot 5 differences in two Christmas tree below:

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

Can you tell a 3D object that has just two surfaces?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

Solve below popular number sequence
314 159 265 358 979 323 846 ?