The calculated distance (air line) between Dortmund and Montignies-sur-Sambre is approximately 150 miles respectively 242 kilometers.
By car or train, the actual journey to Montignies-sur-Sambre is certainly longer, as only the direct route (as the crow flies) between Dortmund and Montignies-sur-Sambre has been calculated here.
Air line (approximately)
242 kilometers
130 nautical miles