Tangram
Assuming that the area of the smallest triangle is one, then the area of the square, the medium triangle and the parallelogram will be two, and the area of each of the two large triangles will be four.
For each number between 1 and 16, try to assemble a convex figure whose area is equal to the number, using an appropriate choice of tangram pieces. Send us your results: math.circle@weizmann.ac.il.