The calculated distance (air line) between Hwangju-ŭp and Sinmak is approximately 30 miles respectively 49 kilometers.
By car or train, the actual journey to Sinmak is certainly longer, as only the direct route (as the crow flies) between Hwangju-ŭp and Sinmak has been calculated here.
Air line (approximately)
49 kilometers
26 nautical miles