From 4:30pm to 8:30pm is exactly four hours. This can be easily calculated two ways: either count ahead in hours from 4:30, or simply subtract 4:30 from 8:30.
9 hours and 30 minutes.
5 hours and 30 minutes.
5.5
1 hour, 10 minutes
9.5
8
5 hours and 15 minutes.
3 hours and 30 minutes.
13 hours and 40 minutes.
4:30pm to 8pm is 3.5 hours or 3 hours 30 minutes.
(8.5+24k) hours where k is an integer.
Eight hours.