Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

If two's company, and three's a crowd, then whats four and five ?

Replace the 'X' with any mathematical symbol to make the expression equal to 111.

18 X 12 X 2 X 3 = 111

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Find the missing number in the sequence below:

Remove two matchsticks to make the below equation correct.

Five thieves looted a bank and they ran away in a car. The bank staff informed the police and they began the search of their car in their jeep. They found them on a road and chased them eventually catching them. The light that is used to fill the number plate was broken on the thieves' car. Also, the headlights of the jeep police were not working. How were the police able to catch the thieves then?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

Cristina was born in 1888. She just had her 30th birthday today how did that happen?