由c=2*圆周率*r,d=2r,得：
r=c/2圆周率
=28.26/(2*3.14)
=28.26/6.28
=4.5(厘米)
d=2r
=2*4.5
=9(厘米)
答:它的半径是4.5厘米,直径是9厘米.