Why 1729 is a magic number? Answer Logically.

What is black when you buy it, red when you use it, and gray when you throw it away?

I speak without a mouth, and hear without ears. I have no-body, but I come alive with the wind. What am I?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

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

Can you tell a 3D object that has just two surfaces?

I get hot but I never sweat,
I cook food but I am not a chef,
I have a door but you can't enter me,
I have a light but I am not a lamp.
Who am I?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?