'half an hour' versus 'a half an hour'

[Iwanna]

Do they mean the same?

Thanks

[Iwanna]

Some examples:

What is Carla doing? She’s been in the garage for a half an hour.
The old town of Chur is a half an hour bus ride away.
I only get a half an hour of TV every other night.
...

[Torsten]

You can either say 'for half an hour' or 'for a half hour'. Both expressions mean the same: for 30 minutes.

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