SSC CGL Model Paper 14

According to the question, ∠BAC =30°
∠BOC = 2 × ∠BAC = 2 × 30° = 60°
(∵ The angle at the centre is twice the angle at the circumference)
In ΔOBC,
OB = OC = radius
∴ ∠OBC = ∠OCB = ∠BOC = 60°
OB =OC =BC
∴ Required ratio = OB : BC = 1 : 1