4/5 kilometre = 0.8 km
If the hike is 4km in total, then the number of times the tent would be swapped is:
(4/0.8) - 1
= 5 - 1
= 4 times (5 is the number of sections of 0.8 km in the 4 km hike however since one person already started with the tent in the first section it would need to be swapped between the two people 4 times - hopefully that makes sense)