Magnetism And Matter

A bar magnet suspended by a horse's hair lies in the magnetic meridian where there is no twist in the hair, on turning the upper end of the hair through \(150^{\circ}\), the magnet is deflected through \(30^{\circ}\) from the meridian. Then the angle through which upper end of the hair has to be twisted to deflect the magnet through \(90^{\circ}\) from the meridian is