Answer: Each Swiss Guard will spend 1 hour 36 minutes on guard duty in one day.
Explanation:
Given: The Vatican has to be guarded 24 hours a day. 
Total Swiss Guards = 15
If they split each day's guard duty equally, the time they will spend on guard duty in one day = (24)÷ 15
= 
 hours
 hours
 hours
= 

= 

Hence, each Swiss Guard will spend 1 hour 36 minutes on guard duty in one day.