The Hexagon And Its Star

Geometry Level 1

Consider a regular hexagon. Extend the alternating sides to get a star.

Which is larger, the yellow area or the blue area?

Yellow area Blue area Equal

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2 solutions

Drex Beckman
Mar 10, 2016

We can determine the interior angles of the hexagon: 4 180 = 720 4 \cdot 180 = 720 and 720 6 = 120 \frac{720}{6} = 120 . Using this, we can conclude the interior angles of the surrounding triangles are 60 degrees: 360 120 2 = 120 360 - 120 \cdot 2=120 , 120 2 = 60 \frac{120}{2} =60 . We can divide 360 by 6 to get 60, and counting there are 6 yellow triangles and 6 blue triangles. Since the blue triangles are equilateral and share one side with the yellow triangles, we know they are equal.

Indeed! We can place this on a triangular grid, and see that the yellow triangles correspond to the blue triangles.

Chung Kevin - 5 years, 3 months ago

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Yeah, nice problem, @Chung Kevin !

Drex Beckman - 5 years, 3 months ago
Forrest Hunter
Mar 14, 2016

Just fold each yellow part to the middle, and you will get the same shape, therefore they are equal.

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