62.8 cm²
Explanation:
Circumference of a circle: 2 x pie x radius
Since the entire perimeter of the square is 80 cm². And a square has 4 sides, you divide it.
80÷4= 20 cm² each side
So if the circle fits perfectly in the square that means it has the same width as the square...which would be 20 cm²...which means 20 cm² diameter.
20 cm² diameter in radius 10 cm² [half of it]
so now you just put it in the formula..
2 x pie x 10= 62.8 cm²