Triangles in a Triangle
An equilateral triangle of side 6 is divided into 36 small equilateral triangles of side 1 by lines parallel to its sides. How many equilateral triangles of any size (pointing up or down) appear in the figure, with sides along the drawn lines? Give an integer.
Related problems & prerequisites
Worth solving first
- Inside the Triangle 4.0/10
- Lattice Points on a Circle 4.0/10
Source: Classic exercise in wide circulation; no traceable original source. Statement written for AxiomIQ.