Jawabanmu

2014-02-11T13:41:15+07:00
k = 62,5 cm 
k = 2 x phi x r
62,5 = 2 x 3,14 x r
r = 62,5 : 6,28
r = 9,95 cm

2014-02-11T13:52:35+07:00
Kll lingkarang = 2πr
62,5 = 2 ×22/7×r
62,5 = 44/7×r
r = 62,5 × 7 / 44
r = 9,9cm