Answer:
246 cm^2
Explanation:
Area of the rest of cardboard = Area of square - Area of the 4 sectors
Kindly note that at each corner of the cardboard, the angle is 90 degrees
Area of square = L^2 = 20^2 = 400 cm^2
Area of a sector = theta/360 * pi * r^2
Since we have 4 sectors;
Area of sectors =4 * 90/360 * 22/7 * 7 * 7
= 22/7 * 49 = 22 * 7 = 154 cm^2
Area of the remaining part of cardboard = 400 cm^2 - 154 cm^2 = 246 cm^2