British penny: 324 mm^2
American penny: 285 mm^2
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35,680mm2
Side = 6 mm Area = 216 mm2 Volume = 216 mm3 Area/Volume = 1 per mm
SA = 34.56 mm2
Not clear which area you want. The surface area of the cylinder can only be determined if you give the length of the cylinder as well as its diameter. As you don't give this I conclude you want the area of the ends only. Each end will be the difference between the area of the 100 mm circle and the 30 mm circle. 100 mm diameter area = 7855 sq mm. 30 mm diameter area = 707 sq mm. Therefore area of end = 7148 sq mm, and you have two ends so total = 14296 sq mm
If your ring has an outer radius of 8 mm and an inner one of 5 mm, you will have pi times (routside)2 minus pi times (rinside)2 or about 122.522 square millimeters of area on the top of the ring. Double that if you add in the surface area of the bottom. As to the sides (the inside and outside), we cannot calculate them without a thickness.