How to get Average for time?

Your problem is that you are trying to add texts and calculate an average of texts, not numbers.

Quick and dirty solution. You can join formulas from separate cells into longer formulas place in single cells.
avg for time 1.png

avg for time 2.png

PKowalik,

That's an alright approach, but it's not really taking advantage of the built in excel date-time values.

You could create a helper column in B1:

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and pull that down, and that would deliver the end result of "count of seconds" just fine.
(I would take this option if I was concerned I'd need to do other kinds of sanitization on the data input).

Conversely,
It would also be possible to select the whole column A,
Then in Data Ribbon => Data Tools Panel => Text to Column
Then just smack the "Next" button in the Wizard three times.

That will tell excel to go and assess the values in column A and apply the same logic testing if they're numbers or times or what that it would apply if you were typing them in fresh.

By doing that, the AVERAGE and SUM formulas will work as expected.

Note that if there are more than 24 hours in a sum it will role the date over and silently be 1 day + time,
so the cell should be custom formatted to "[h]:mm:ss" to force it to show total number of hours, even if it's more than 24.

@ben_hensel
You are absolutely right. I just like maths and I keep forgetting how date/time data are handled internally in Excel .
Anyway, I thought a moment and in my opinion even a helper column is not necessary.
Array formulas
=SUM(TIMEVALUE(A2:A12))
=AVERAGE(TIMEVALUE(A2:A12))
will do the job, too (with formatting as you described, of course).