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TopNewestReferring to the 4 piece assemblies (red, blue, yellow, green pieces), it only looks like 3 sided triangles are formed in each case, with one extra square in the 2nd. But in fact the slope of the red piece is 0.375 while the slope of the blue piece is 0.400. Consequently, the first figure is actually not a convex figure, while the 2nd figure bulges outward. The difference is just enough to account for that extra square.

In other words, do the math, and don't just trust what your eyes say.

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See this .

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