Can you find the key in the picture below?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

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?

What makes this number unique: 8,549,176,320?

Look at the picture and find out which square is not linked with any of the other squares.

Spot 5 differences in two Christmas tree below:

Which is heavier: a ton of bricks or a ton of feathers?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?

How many times can you subtract the number 5 from 25?

A mathematician couple was having a Frappuccino in Starbucks sitting opposite to each other. Suddenly the guy noticed the text written on the paper in front of them and exclaimed that it was wrong. The girl denied it and said it is appropriate. Both are correct. What is written on the paper?