Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

What is the largest number you can write with just 3 digits?

Whats the next number in the below number sequence pattern.

You need to remove two matchsticks to make the below equation true. Can you do it ?

What question can you never answer yes to?

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?

If "P" means "-", "Q" means "/", "R" means "+", and "S" means "*" then find the value of the following:

21 Q 7 R 9 S 10 P 13

Count the number of triangles in the below picture?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

Which is faster, Heat or Cold ? Explain.