4
8 hours.
4 + 24k where k is any integer.
The time from 0530 to 1230 is 7 hours. To calculate this, you can subtract 0530 from 1230: 1230 - 0530 = 0700, which equals 7 hours.
3.5 hours.
20.5 hours.
Four
4
It is 4 hours.
9 hours and 30 minutes.
201/2 hours exactly.
1960
It is 4 hours and 15 minutes.