7 and 1/2 hours
8 hours.
12am to 4pm is 16 hours.
6 hours from 4pm to 10pm
Nine hours.
840
Nine and a half hours.
4.5 hours
ten and a half
7am to 4pm is 9 hours.
It is (8.5 + 24k) hours where k is an integer.
8:30am to noon is 3.5 hours.
4pm to midnight is 8 hours.