The calculated distance (air line) between Bourg-la-Reine and Longjumeau is approximately 6 miles respectively 10 kilometers.
By car or train, the actual journey to Longjumeau is certainly longer, as only the direct route (as the crow flies) between Bourg-la-Reine and Longjumeau has been calculated here.
Air line (approximately)
10 kilometers
5 nautical miles