The ratio of magnetic moments of two short magnets which give null deflection in Tan B  position at 24 cm and 18 cm from the centre of a deflection magnetometer is

At the Tan B position , the strength of the magnetic moment at the magnetometer is proportional to the cube of the distance between the magnetometer and center of deflection of the magnetometer.∴M1d13=M2d23 ⇒M1M2=d1d23 ⇒M1M2=24183 ⇒M1:M2=64:27