There are 14 hours and 45 minutes between 3:45 pm and 6:30 am.
There are 9 hours between 630 am and 930 am.
9 hours.
9 hours.
8.5
7 and a half hours
10.5 hours
11 hours and 45 minutes.
11 hours and 45 minutes.
(11+24k) hours where k is an integer.
630 PM
If they're both on the same date, then they mark a period of 21/2 hours.