How do I add numbers to time? I have a start time in time format of 7:30 a.m.
I calculate a project will to 4.25 hours, in general number format, i.e., 4
hours and 15 minutes. When I add the two, it does not give me 11:45 a.m., but
instead it still shows 7:30 a.m. I tweaked with the format in the results
cell to no avail.

Hi,
When you add numbers to time, XL treats those numbers as days, so you need
to divide by 24 if you want hours.

If 7:30 AM is in A1...
=A1+(4.25/24)
Format like A1

Regards - Dave.