Can you replace the question mark with the correct number?

Solve below rebus puzzle?

Identify the hidden meaning behind this picture?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

What is 3/7 chicken, 2/3 cat and 2/4 goat?

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?

The cream is heavier than Milk. True or False?

What always comes into a house through the keyhole?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?