Four glasses sit side by side.
At first glance, they appear almost identical.
Each contains water.
Each contains a different object.
And the water levels seem surprisingly similar.
Glass A contains a paperclip.
Glass B contains a baseball.
Glass C contains an eraser.
Glass D contains a wristwatch.
Then comes the question:
Which glass actually contains the most water?
It sounds easy.
But before answering, look carefully.
The biggest object may grab your attention first.
The water levels may make all four glasses appear nearly equal.
Yet one small scientific principle changes everything.
Don’t Let the Water Level Fool You
Your eyes naturally focus on what is most visible.
In this puzzle, that may be the baseball.
It’s large.
It’s obvious.
And compared with the tiny paperclip, it occupies a significant portion of the glass.
But the puzzle isn’t asking which glass contains the largest object.
It’s asking:
Which glass contains the most water?
That difference matters.
The Answer Depends on Water Displacement
When an object is submerged in water, it occupies space that water cannot occupy at the same time.
This is the basic idea behind displacement.
The amount of water displaced depends on the volume of the submerged portion of the object.
A large submerged object generally displaces more water than a small submerged object.
So if the puzzle assumes identical glasses, comparable displayed water levels, and fully submerged objects, the size of the objects becomes the key clue.
Now Compare the Objects
The baseball occupies a large amount of space.
The wristwatch occupies less.
The eraser is smaller still.
Then there’s the paperclip.
Compared with everything else, it takes up very little space.
That means it displaces the least water.
Under the intended assumptions of this classic puzzle, that leads to the answer:
Glass A—the glass containing the paperclip—has the most water.
Why?
Imagine removing every object without spilling any water.
Take out the baseball.
Remove the watch.
Lift out the eraser.
Finally, remove the paperclip.
The object that occupied the least submerged volume left the most room for water.
That’s the paperclip.
The principle is simple once you see it.
The Baseball Creates the Opposite Effect
Because the baseball occupies much more space inside the glass, it displaces more water.
Its glass can therefore appear filled to a similar level while actually containing less water than the glass holding the tiny paperclip.
This is the trick.
Your eyes see water height.
The puzzle asks you to think about volume.
But There’s an Important Assumption
Like many internet puzzles, the drawing may not provide enough information for a rigorous real-world measurement.
To reach the intended answer, we generally assume that the glasses are identical, the relevant objects are submerged as shown, and the illustrated water levels are meant to be comparable.
If those conditions changed, the answer could change too.
For example, an object that floats is governed by a slightly different comparison because only part of it is submerged.
That’s why the exact wording and illustration matter.
Real Science Requires Precise Information
Suppose the water levels weren’t actually equal.
Or one glass had a slightly different shape.
Perhaps an object was only partially submerged.
Then simply choosing the smallest visible object wouldn’t necessarily solve the problem.
In an actual experiment, you would measure the quantities rather than relying on a drawing.
But as a visual brain teaser, the intended principle remains clear:
The smaller submerged object displaces less water.
Why Do So Many People Hesitate?
Because the puzzle encourages quick visual judgment.
Your brain doesn’t begin by calculating volume.
It sees four glasses and four objects.
The baseball immediately demands attention.
The watch is familiar and visually complicated.
The eraser is easy to recognize.
Meanwhile, the paperclip sits quietly at the bottom.
It’s almost too small to matter.
And that’s precisely why it matters.
The Smallest Detail Holds the Key
Visual puzzles frequently work this way.
They give you something obvious to look at while hiding the useful clue somewhere less dramatic.
Your attention moves toward the largest feature.
But solving the puzzle requires stepping away from what looks important and asking what actually affects the answer.
In this case, that’s displacement.
Try a Simple Thought Experiment
Imagine an empty glass.
Now pour water into it until it reaches a particular line.
Next, lower a large object into the water.
What happens?
The water level rises because the object occupies space.
If enough water was already present, some could even overflow.
Now repeat the experiment with a tiny paperclip.
The water level changes far less because the paperclip occupies much less volume.
That’s the puzzle in its simplest form.
The Object Doesn’t “Create” More Water
This is another important distinction.
Putting something into a glass can make the water level rise.
But it hasn’t created additional water.
The object simply occupies some of the glass’s volume.
That’s why judging quantity only from the height of the water can be misleading when different-sized objects are inside.
Displacement Is Everywhere
This principle isn’t limited to puzzle illustrations.
Place ice into a drink and the liquid level changes.
Step into a full bathtub and the water rises.
Lower an object into a container of liquid and it displaces an amount related to its submerged volume.
The principle becomes far more interesting when combined with buoyancy and density, but the basic observation is easy to demonstrate.
And That’s Why This Puzzle Works So Well
You don’t need advanced mathematics.
You don’t need a calculator.
You don’t need specialized scientific equipment.
You simply need to recognize that two glasses can show similar water levels while containing different actual quantities of water if differently sized objects occupy space inside them.
Once that clicks, the puzzle becomes much easier.
But There’s Another Reason People Share It
The science is only half the fun.
The other half is seeing how people approach the question.
Some answer immediately.
Others carefully compare every object.
Some search for a hidden trick.
Others assume the obvious answer must be wrong simply because it’s a puzzle.
That difference in reasoning can be more interesting than the answer itself.
THE STORY CONTINUES ON THE NEXT PAGE… 👇👇👇
