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

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

A man wants to cross the pit of fire which is 25 feet in length and he has 2 planks(fire resistant) 19 feet in length. How can he cross the pit of fire alive?

Why did the Girl throw the butter out of the window?

Can you find out the remainder when 3^300 is divided by 5?

How many Watermelons are there in the below picture?

Astrology starts with the alphabet A, Biology starts with B, Psychology with P and Limnology with L.

Can you find an "ology" that begins with a P?

There are three light switches outside a room. One of the switches is connected to a light bulb inside the room.
Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

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