Question 15
The two figures below are composed of small equilateral triangles of the same size. We want to put several pieces of the parallelogram cardboard (which can be rotated or flipped that is shown on the left) into the equilateral triangle grid that is shown on the right without overlapping each other. The sides of these parallelogram cardboards are required to be placed along the grid lines of the equilateral triangle grid and cannot exceed the sides of it. What is the maximum number of pieces of parallelogram cardboard that can be placed into the triangular grid? Justify your answer and show one way to place the cardboards.
