The fifth grade, the second volume, mathematics supplementary exercise, page 78, the answer is urgent ~
1. perimeter C=πd, d=2cm, square area s = d * d = 4cm2.
2. The topic requires that the area diameter of a circle (iron cover) is D = 30+ 10 = 40cm, R = D/2 = 20cm, and S = π * R * R = 1256cm2.