Difficulty: Tricky

Gertrude has a collection of shapes that she likes to arrange in patterns.

She starts with a regular hexagon with 10 cm sides, and three regular triangles that also have 10 cm sides.

She arranges the triangles around the hexagon, and then lines them up. In the end, one side of each triangle is lined up with a side of the hexagon. They are evenly spaced, with a triangle against every second edge of the hexagon.

How many sides does this final shape have?

Scroll down or click for a hint, or the answer!

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Brainteaser hint

1. Regular shapes have sides of the same length, and all the inside angles are equal.
2. Shape puzzles are usually a lot easier if you try drawing them!
3. Remember that you can divide a hexagon into six regular triangles by drawing lines from the corners to the centre.

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Brainteaser answer

Gertrude’s shape has three sides. It’s a regular triangle with 30 cm sides!

Large triangle with smaller trangles marked in its points.

Did you know?

Regular triangles are more commonly called equilateral triangles.

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