Cut out the largest circle from a square sheet of iron with a side length of 20 cm. What is the area of the remaining sheet of iron in the original square? Requirements: to calculate the formula, you must write the unit!

Cut out the largest circle from a square sheet of iron with a side length of 20 cm. What is the area of the remaining sheet of iron in the original square? Requirements: to calculate the formula, you must write the unit!

The largest circle on the square should be the inscribed circle of the square, the area of the square = 20 * 20 = 400 square centimeters
The area of inscribed circle = (20 / 2) * (20 / 2) * 3.14 is about 314 square centimeters
The remaining area = 400-314 = 86 square centimeters
The remaining area of the square = 86 / 400 = 43 / 200
{(square of side length of square - square of radius of circle * 3.14) / square of side length of square} = 43 / 200