R=5dm, perimeter = 2π× 5 =10π = 31.4 (DM), area =π×5? =25π=78.5(dm？ ) d=6cm, perimeter =π×6=6π= 18.84(cm), area = 1/4×π×6? =9π=28.26(cm？ ) 1. The diameter of the inscribed circle of the square is equal to the side length, so the radius r=2m. Is the area of the flower pond πr? =4π. The flower bed area is 4×4= 16, so the ratio is 4 π: 16 = π: 4 = 0.785.

2. The area of the big circle minus the area of the small circle.

π(50+2)? - π50? =204π=640.56(m？ )