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Which Glass Has More Water? This Simple Picture Puzzle Is Trickier Than It Looks
At first glance, the image appears to be a straightforward visual puzzle. Four identical-looking glasses are filled with water, but each contains a different object: paper clips, baseballs, an eraser and a wristwatch.
The question is simple:
Which glass contains the most water?
The answer may seem obvious once you think about what is actually occupying space inside each glass.
Look Beyond the Water Level
The four glasses are labeled A, B, C and D.
Glass A contains paper clips.
Glass B contains several baseballs.
Glass C contains an eraser.
Glass D contains a wristwatch.
The key to solving the puzzle is not simply comparing the objects by their appearance. Instead, you need to consider how much physical space each object takes up inside the glass.
Every object placed into water displaces some amount of water according to the volume of the object that is submerged.
That means the larger the object, the more space it occupies—and, assuming the glasses contain the same overall amount up to the shown level, the less actual water remains.
The Likely Answer: Glass A
The best answer is A — the glass containing the paper clips.
Why?
Paper clips are relatively thin and occupy very little volume compared with the other objects shown.
The baseballs in Glass B occupy considerably more space. The eraser in Glass C also takes up more volume than the paper clips, while the wristwatch in Glass D has a larger overall volume as well.
So if the water level is intended to be the same in each glass, the glass containing the object with the smallest displaced volume will contain the greatest quantity of water.
That makes Glass A the logical choice.
Why the Baseballs Are a Trap
Many people immediately choose Glass B because they see several baseballs surrounded by water and assume that a larger visible water area means more water.
But the baseballs are exactly what make this option deceptive.
A baseball has a substantial volume. When several baseballs are placed inside a glass, they occupy a significant amount of the space that could otherwise be filled with water.
The water rises around them because the balls displace it.
So even though the glass may appear to contain a lot of water, some of the space inside the glass is actually occupied by the baseballs.
What About the Eraser?
Glass C is another tempting option.
The eraser is smaller than a baseball, but it is still a solid object with a considerable volume compared with a few thin paper clips.
If the water reaches the same level in each glass, the eraser means that some of the glass’s capacity is occupied by the eraser rather than water.
Therefore, C would not beat A under the puzzle’s intended assumptions.
And the Watch?
The wristwatch in Glass D can make the puzzle even more confusing.
A watch is relatively compact, and someone might argue that it could displace less water than the eraser or baseballs.
But the comparison is about the actual volume of the objects, not how visually large they appear.
A watch contains a case, mechanism, strap and other components. Depending on exactly how much of it is submerged, it can displace more water than the very thin paper clips.
The paper clips therefore remain the strongest answer.
The Science Behind the Puzzle
The principle involved is called displacement.
When an object is placed into water, it occupies physical space. The water cannot occupy exactly the same space at the same time, so it moves upward or outward around the object.
This is closely related to the principle commonly associated with Archimedes.
For a completely submerged object, the amount of water displaced corresponds to the object’s submerged volume.
For example, imagine two identical containers filled to exactly the same height.
If one contains a large rock and the other contains a tiny metal clip, the container with the tiny clip can contain more actual water because the clip takes up less space.
The same basic idea applies to this puzzle.