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2025 Math Kangaroo

Problem 4

Problem 4 · 2025 Math Kangaroo Easy
Geometry & Measurement area-fractiongrid-counting

The regular hexagon shown is divided into a number of triangles of equal area. What fraction of the hexagon is grey?

Figure for Math Kangaroo 2025 Problem 4
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Answer: B1⁄3
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Hint 1 of 2
Every little triangle in the picture has the same area, so the answer is just (grey triangles) over (all triangles).
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Hint 2 of 2
Count the grey triangles, then count the total, and reduce the fraction.
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Approach: count equal-area triangles, then reduce
  1. All the small triangles have equal area, so the grey fraction is simply how many are grey out of how many there are.
  2. The hexagon is cut into 24 equal triangles, and 8 of them are shaded grey.
  3. So the grey part is \(\frac{8}{24}=\frac{1}{3}\) of the hexagon, which is (B).
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