Why Aeroplane windows are round?

What word is represented by this rebus?

Can you find out which options fits best with the missing column?

Can you count the number of triangles in the given picture?

I am thinking of a five-digit number such that:
The first and last digits are the same, their submission is an even number and multiplication is an odd number and is equal to the fourth number. Subtract five from it and we obtain the second number. Then divide into exact halves and we get the 3rd number.

What number I am thinking of?

Why is the Hole below a Lock?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

A maths symbol is hidden in the below Bar Graph. Can you decipher it?

What has a bottom at the top?

The more you take me, the more you leave me behind.
Who Am I?