Replace the question mark with the number below given a simple math problem.

I organized a small get together at my home.
In the party , i have a barrel with some whiskey in it.

Suddenly Guest 1 say 'I bet this barrel of whiskey is more than half full'.
'No, it's less than half full' Guest 2 replied.

I don't have any measuring instrument and without removing whiskey from it , how can i determine which of the guest is right ?

What occurs twice in a week, once in a year but never in a day?

My location can be determined by the below rebus.
So where am i ?

A man is found hanging dead from the ceiling of a room. The room’s dimensions are 15 x 15 x 15. The man is only 6ft tall and the rope was only 2ft long. There are no windows and only one door to the room. The door is bolted shut from the inside, and a puddle of water is under the man. How did he kill himself?

Can you find the 09 errors in the picture below?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

What is at the end of a rainbow?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

Can you find the next number in the below sequence
3 , 7 , 10 , 11 , 12 , 17 ?