IF they're both on the same day, then they're 5hours 10minutes apart.
From 6:15pm to 7:15am is 13 hours.
2 hours.
21 hours
There are 16 hours from 4 am to 8 pm. 4 am to 4 pm is 12 hours, then 4 pm to 8 pm is another 4 hours.
There are 11 hours from 12 PM to 11 PM. You can count the hours starting from 12 PM: 1 PM, 2 PM, 3 PM, and so on, up to 11 PM.
10 hours and 45 minutes.
7:45 am to 6:15 pm is 10 hours 15 minutes (101/4 hours)
There are 10.25+24k where k is an integer.
From 8am to 6:15pm is 10 hours and 15 minutes.
6:15am to 5pm is 10 hours and 45 minutes.
8.5 + 24k hours where k is any integer.
From 6:15am to 1:30pm is 7 hours and 15 minutes.
There are 9 and 1/2 hours between 8:45 am and 6:15 pm.
From 7:45 AM to 6:15 PM is a total of 10 hours and 30 minutes. To break it down, there are 10 hours from 7:45 AM to 5:45 PM, and then an additional 30 minutes from 5:45 PM to 6:15 PM.
13 + 24k hours where k is an integer.
From 6:15pm to 7:15am is 13 hours.
From 2:37 am to 6:15 am is 3 hours and 38 minutes. From 2:37 am to 6:15 pm is 15 hours and 38 minutes. From 2:37 pm to 6:15 pm is 3 hours and 38 minutes. From 2:37 pm to 6:15 am is 15 hours and 38 minutes.