(c) 33.33%
When an equilateral triangle is cut from its three vertices to form a regular hexagon then out of the 9 equilateral triangles that form ΔABC, three triangle, ΔADE, ΔFCG,ΔIHB are cut off and 6 remain in the hexagon.
This means that \(\frac{1}{3}\) rd of the area has been removed or wasted to get the hexagon.
∴ Area wasted = \(\bigg(\frac{1}{3}\times100\bigg)\)% = 33.33%