At first glance, the puzzle looks almost too easy.
Four identical glasses—A, B, C, and D—are filled to roughly the same level. Inside each glass, however, is a different object: a paperclip, a baseball, an eraser, and a wristwatch.
The question is simple:
Which glass actually contains the most water?
Most people instinctively focus on the visible waterline. Since the glasses appear equally full, it is tempting to assume they all contain the same amount.
But the objects inside change everything.
When an object is submerged in water, it takes up space and displaces some of the liquid. The larger the object, the more volume it occupies inside the glass—and therefore the less actual water the glass can hold while maintaining the same visible level.
That means the solution depends on identifying the smallest object.
Glass A contains the paperclip.
Glass B contains the baseball.
Glass C contains the eraser.
Glass D contains the wristwatch.
Of the four, the paperclip takes up the least space.
So even though all the glasses appear similarly filled, Glass A contains the greatest amount of actual water.
The baseball in Glass B displaces the most, meaning that glass contains the least water. The eraser and wristwatch fall somewhere in between.
The answer: Glass A
What makes the puzzle interesting is how easily our eyes can mislead us. We tend to judge what we see on the surface—the height of the water—without immediately accounting for what is hidden beneath it.
It is a small reminder that appearances do not always reveal the whole picture.
Sometimes the correct answer comes only when we stop looking at what seems obvious and start asking what else is taking up space.
