Only one colour, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

In the picture that is attached with this question, you can find a square which comprises of four little squares inside it. Consider this square to be made with matchsticks. You have to remove two matchsticks such that only two squares remain instead of five.How will you do it ?

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

I add 5 to 9 and get 2. The answer is correct, so what am I?

What three numbers, none of which is zero, give the same result whether they’re added or multiplied?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Look at me. I can bring a smile to your face, A tear to your eye, Or even a thought to your mind. But, I can't be seen. What am I?

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?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?