The calculated distance (air line) between Chhāgalnāiya and Serchhīp is approximately 87 miles respectively 140 kilometers.
By car or train, the actual journey to Serchhīp is certainly longer, as only the direct route (as the crow flies) between Chhāgalnāiya and Serchhīp has been calculated here.
Air line (approximately)
140 kilometers
75 nautical miles