Given a square piece of metal of side length 6cm
If a circular plaque of diameter 6cm is cut from the metal piece, the area wasted is the shaded area in the diagram below:
Total Area of the Metal Piece = 6 x 6 = 36 square cm
Area of the Circular Plaque
Therefore:
Area of the Shaded Portion=Area of Metal Piece-Area of circular Plaque
The percentage of metal that was wasted will then be:
The percentage of metal that is wasted is approximately 21.5%.