The calculated distance (air line) between Hwangju-ŭp and Kanggye is approximately 165 miles respectively 265 kilometers.
By car or train, the actual journey to Kanggye is certainly longer, as only the direct route (as the crow flies) between Hwangju-ŭp and Kanggye has been calculated here.
Air line (approximately)
265 kilometers
143 nautical miles