3 hours 53 minutes
About 30 minutes
I do it in two parts. I calculate how much time has elapsed between the AM and noon, then how much time has elapsed between noon and the PM, then add them together.
6 hours have been elapsed
The elapsed time of 1 pm to 9 am is 20 hours.
45 minutes before 6:30 PM is 5:45 PM.
1:45 plus 15 minutes gives us 2:00 pm. It is nine hours from 2:00 to 11:00 pm. Then we have 23 more minutes we can add to the first 15 for 38 minutes. 9 hours and 38 minutes is the elapsed time.
15 + 24k hours and 53 minutes where k is any integer.
About 30 minutes
6 hours, 45 minutes has passed from 10:00 PM to 4:45 AM.
10:38 AM was.
I do it in two parts. I calculate how much time has elapsed between the AM and noon, then how much time has elapsed between noon and the PM, then add them together.
18 minutes
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.
6 hours have been elapsed
255
The elapsed time of 1 pm to 9 am is 20 hours.
2 hours, 22 minutes.