There are a variety of modern definitions of economics, some reflect evolving views of the subject or different views among economists.
So the area of the square is 7 x7 = 49 cm^2 and the perimeter of the square is 7 x 4 = 28 cm. And in example 1 you have a square of side length 8cm and you need to work out the area and perimeter of the square. So the area of the square is 8 x8 = 64 cm^2 and the perimeter of the square is 8 x 4 = 32 cm.
For example, if you are given the area of a circle as 12.56 square meters then you can find its radius is 2 meters, but this is due to the shape. To contrast, consider that a square with area 12.56 square meters has a side length of about 3.54 meters and a perimeter of 14.18 meters.