I looked at a couple of similar questions but have not been able to achieve a
good result.

I have a few cells defined as Time HH:MM. I want to sum them up so I get
hours and minutes. In the cell to hold the total, I used "=SUM(N43:N47)". I
formatted the Total cell as custom with a format of [hh]:mm. The original
values were 10:00, 3:00, 12:00. I was expecting to get 25:00. What I am
getting is 577:00

Which is funny, but not very useful.

Can you help, Ed