I make zippers for a living. Every few months we produce enough zipper to go around the world, which is 40,075.16 kilometers at the equator.
One day I’m bored. I haul out 40,075,160 meters of zipper (over 700 tons) from the warehouse, and make a perfect, tight wrap around the equator.
I smile in satisfaction. Upon inspecting my work, I find that the zipper is on the ground and on the surface of the ocean, getting dirty and wet, which is obviously unacceptable. Being the fickle person I am, I decide to haul in more zipper from the warehouse, and raise the entire zipper loop one meter above ground level (and sea level).
The math is relatively straightforward. However, before you work out the answer with some pencil and paper, based purely on your intuition, estimate roughly how much more zipper I need.
To help out, here is a quick guide:
1%: 400 kilometers
10%: 4,000 kilometers
100%: 40,000 kilometers
You have 10 seconds to make a guess. Ready?
Note: Illustrations from WHAT IF?: Serious Scientific Answers to Absurd Hypothetical Questions by Randall Munroe. Copyright©2014 by xkcd Inc. Used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Afterword: As you can see, I have taken the time to ask for permission from the publisher before using someone else’s work, even if they are only stick figures drawings. Sometimes all you need to do is ask (click for full image).