The maximum size is when the sides of the square are equal to the radius of the circle, r, containing the sector. The sector is one quarter the area of the circle so it's (pi)r^2/4. The radius and side of the square are both 24cm and the area of the square is r^2, so the wastage is r^2-(pi)r^2/4=(1-((pi)/4))r^2=0.2146*576=123.61sq cm.