Jawabanmu

2014-02-18T23:05:45+07:00
52,2 X 7/22 = 16,6 : 2= 8,3  cm .... 
2014-02-18T23:35:44+07:00
K = \pi.d
55,2 = 3,14.d (pindah ruas)
d = 55,2/3,14 
d = 16,6

r = d/2
r = 16,6/2
r = 8,3