The calculated distance (air line) between Côte-Saint-Luc and Longueuil is approximately 10 miles respectively 16 kilometers.
By car or train, the actual journey to Longueuil is certainly longer, as only the direct route (as the crow flies) between Côte-Saint-Luc and Longueuil has been calculated here.
Air line (approximately)
16 kilometers
9 nautical miles