The calculated distance (air line) between Ar Rumaythah and Al Mishkhāb is approximately 46 miles respectively 74 kilometers.
By car or train, the actual journey to Al Mishkhāb is certainly longer, as only the direct route (as the crow flies) between Ar Rumaythah and Al Mishkhāb has been calculated here.
Air line (approximately)
74 kilometers
40 nautical miles