Hi!

In my textbook, there is such an example sentense.

Sen ciddi bir oğrenciydim.

My question is regarding the "bir".

I think we can remove this part, so I´m interested in the difference in the meaning with "bir" and that without it.

Thank you in advance!

´´Sen ciddi bir oğrenciydin.´´ m must be ´´n´´. 

You can say that ´´Ben ciddi bir öğrenciydim.´´ and cannot say that ´´ Ben ciddi bir öğrenciydin.´´ 

Your text book is wrong or you make a mistake in writing.

´´Sen ciddi öğrenciydin.´´ Actually, it does not sound good.

You are a student. 

You are student.  

´bir´ means ´´a´´.

Would these also be an alternative translation?

"You were a genuine student"  

"You were a legitimate student"

"You were a serious student"

It´s meant to be past tense?