Excel weekly planner

I am creating a weekly planner for an excel class that I am taking.
Each cell is in half hour increments. I have to plan out my week with work, school, homework etc.
I would like to total the time spent on each task.
Is there any way to give each individual cell a time value of 30 minutes, then create a formula to add all time spent on that task.
By this I mean if 9 cells that says "homework" would be 4.5 hours total.
I hope I am clear in my explanation. Any help would be appreciated.

Thank you for the super fast reply!
I believe that will work. Just one more thing, it counts the number of cells (sleep = 9) But that is 9 half hours.
How would I multiply it by 2 to show it as 4.5 hrs, or would I divide it by 2?

Thank you I actually figured it out on my own before you replied. (Trial and error)
I do appreciate your help.
Thanks again!

@ ampman337

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