A circular flower bed with a diameter of 8cm and a radius of (0.04? ) m, its perimeter is (0.08x3.14 = 0.2512) m, and its area is (0.0016x3.14 = 0.005024) m2.
Bend a 6.28dm long iron wire into a circular iron ring. The diameter of this iron ring is (6.28/3. 14=2? ) dm, the area is (1?
X3. 14=3. 14) square decimeter.
The radius ratio of circle A to circle B is 5:3, and the perimeter ratio is (? 5? : 3), area ratio (? 25:9)
(Note: π is approximate value 3. 14)