What is the fastest way to double your money?

In the picture given below, can you find out which digit will take place of the question mark?

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

In a town, there are over 100 flats.
Flat-1 is named first flat.
Flat-2 is named second flat.
Flat-3 is named third flat.

A visitors 'Victor' decides to walk through all the flats, he finds all the flats except flat-62.
Victor later founds that the local of the town have given it another name.

What is the name of the Flat?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

A girl was standing near the window thinking something. All of a sudden she decides something and throws something out of the window. She dies very soon after throwing it. She was perfectly healthy and had no disease or allergy. No one killed her and she did not commit suicide.

Can you think of any possible explanation that is logical as well for what happened there?

A kind heart person buy packed food at 3$/packet from United states and sells them at 1$/packet at Africa. After some time he becomes a millionaire.

How come the guy become millionaire ?

Two girls were born to the same mother, on the same day, at the same time, in the same month and year and yet they're not twins. How can this be ?

As shown in the image, the nine Dogs are square fenced. By constructing just two square fences can you make sure that two Dogs cannot meet each other without crossing the fence?

When you stop to look, you can always see me. But if you try to touch me, you can never feel me. Although you walk towards me, I remain the same distance from you. What am I?