Black Changes its Colour

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




Similar Riddles

In a school, 280 students studied chemistry, 254 students studied physics and 280 students studied biology.

97 students studied chemistry as well as physics, 138 students studied physics as well as biology and 152 students studied chemistry as well as biology.

73 students studied all the three branches.

Can you find out the total number of students?

Asked by Neha on 17 Jun 2026


In a science lab, a petri dish hosts a healthy colony of yeast for an experiment. Now every minute, all the yeast cells divide into two. At noon, there was just a single cell of yeast and at 1:22, the Petri dish was half full. Can you calculate when the dish will be full of yeast?

Asked by Neha on 23 Jun 2021

There are four people in a house. A fireman, an athlete, an old woman, and a drunk guy. The house catches fire and before the fact is known, it is too late. All they know is that the entire house is in flames and it will collapse exactly after twelve minutes. Now they can move out of the house but for that, they will have to pass the hallway which is entirely blazing with flames. Thus to move, one must carry a fire extinguisher to keep the flames away. Seeking the burnt wooden floor, only two people can run through that hallway at one time. But for others to go, one must return back with the fire extinguisher. The fireman is trained for such tasks and can run through the hallway in a minute. The athlete can make it in a couple of minutes. The old woman can run slowly and will cover the hallway in four minutes. The drunk guy will take five minutes to run through it. If all of them can make it through the hallway in twelve minutes, all of them will be saved. When two move together, they will run at the speed of the slower ones.

How will all four of them manage to run to safety?

Asked by Neha on 02 Jun 2023


Can you replace the question mark with the correct number in the below table sequence?

Complete the table Sequence

Asked by Neha on 23 Feb 2025

Find the missing number in the sequence below:

Find the missing number

Asked by Neha on 03 Sep 2021

I am white when I am dirty, and black when I am clean. What am I?

Asked by Neha on 31 Mar 2022


What can go up a chimney down, but can’t go down a chimney up?

Asked by Neha on 12 Jul 2025

Can you make a six-letter word using the letters N, A and B ?

Asked by Neha on 29 Aug 2021

Bay of Bengal is in which state?

Bay of Bengal

Asked by Neha on 12 Mar 2021


Find the next number in the sequence

5 12 24 36 ?

Asked by Neha on 08 Jul 2023

Hot Articles

Amazing Facts

Gambling

In Canada, a mathematical puzzle must be solved in order to win the lottery to classify it as a “game of skill” not gambling.