The force between two bar magnets whose centers are d metres apart is 4.8N. When the separation is made 2d the force is reduced to (a) 2.4 N (b) 1.2 N (c) 0.6 N (d) 0.3 N

Force is inversely proportion to sq. Of distance so the force become 1/4 hence the answer is 1.2 newtons

Since it`s a bar magnet, it can be treated as magnetic dipole. Force due to dipole is inversely proportional to r^3. Hence the, as the distance becomes twice, force will become 1/8 times.