The calculated distance (air line) between Kangdong-ŭp and Pyongyang is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Pyongyang is certainly longer, as only the direct route (as the crow flies) between Kangdong-ŭp and Pyongyang has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles