The calculated distance (air line) between Munsan and Yangp'yŏng is approximately 46 miles respectively 74 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Munsan and Yangp'yŏng has been calculated here.
Air line (approximately)
74 kilometers
40 nautical miles