Wolfram Demonstrations Project

Consider a grid of 25 rectangles of dimension 9×11 in portrait view that cover an area of 25×9×11=2475.

The second grid is made up of 24 rectangles of dimension 11×9 in landscape view—that cover the same area!

To understand what happened to the missing 9×11 rectangle, see the Details.

Contributed by: Ed Pegg Jr

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The first grid has overall dimensions 45×55 for an area of 2475. The second grid has overall dimensions 44×54 for an area of 2376. The difference is 99, which is small visually compared to the areas of the two large rectangles. This is known as the melting tile illusion.

Cells of size