She should write 5.5 hours on her time card.
To write 5 hours and 30 minutes on her time card, she can simply write 5.5 hours. This is because 30 minutes is half of an hour, so it can be represented as 0.5 hours.
It would actually depend on the way that you want your result. It can be in h, min, s
For example, in hours it would be 5.5h
in minutes, 330min
in seconds, 19800s
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