no 20 tolong dijawab,pke cara kak:)

r : R = 4 : 5

Kb = 88 cm

Kb = 2 × phi × R
88 = 2 × 22/7 × R
88 = 44/7 × R
R = 88 : 44/7
R = 88 × 7/44
R = 14 cm

r : R = 4 : 5
r = 4/5 × R
r = 4/5 × 14
r = 11,2 cm

d k = 2 × r
d k = 2 × 11,2
d k = 22,4 cm (c)

keterangan :
r = jari-jari lingkaran kecil
R = jari-jari lingkaran besar
Kb = keliling lingkaran besar
d k = diameter lingkaran kecil