the strength of a bar magnet's magnetic field decreases with distance according to what is known as an inverse cube law; multiplying the distance from the magnet by a factor of $k$ divides the magnetic field strength by a factor of $k^3$. suppose the magnetic field strength of the magnet is $64 \text{ gauss}$ at a distance of $10 \text{ cm}$ away. what is the magnetic field strength of the magnet, $20 \text{ cm}$ away?