There are 4 hours between 8:30 am and 12:30 pm.
Nine hours.
There are 6 hours and 30 minutes from 8-1230pm to 230pm.
1960
8 hours.
4.5 hours
840
Nine and a half hours.
That is eight hours.
ten and a half
There are 4 and 1/2 hours between 8:30 and 1.
If those two times are both in the same day, then the period between them is 121/2 hours long.
It is (8.5 + 24k) hours where k is an integer.