Jika titik O merupakan pusat lingkaran, luas juring AIB = 31, 4 cm², dan besar sudut AOB=100°, diameter lingkran adalah...

luas lingkaran = luas juring/(100°/360°)
(phi) × r^2 = 31,4 × 360°/100°
(3,14) × r^2 = (31,4 × 360°)/100°
r^2 = (31,4 × 360°)/(3,14 × 100°)
r^2 = (10 × 360°)/(100°)
r^2 = 360°/10°
r^2 = 36
r^2 = 6^2
r = 6 cm

diameter
= 2 × r
= 2 × 6
= 12 cm