'Couple' vs 'Couple of'

[Tom]

Hi

Could you please tell me if the following sentences (information) are correct?

1- I met him a couple days ago. (informal)
2- I met him a couple of days ago. (formal)

1- He has a couple books. (informal)
2- He has a couple of books. (formal)

Tom

[Yankee]

Hi Tom

To be honest, I don't really see much (if any) difference in the sense of formality, however the use of the word "of" may be seen as more "formally correct" grammatically.

I hope you understand what I mean.

Amy

[Tom]

Thanks Amy!

Which one you (Americans) prefer, Amy?

Tom

[Yankee]

Hi Tom

I think they are used interchangeably. In spoken American English "couple of" frequently sounds like "coupla".

Gimme a coupla minutes, will ya?

Translation: Give me a couple of minutes, will you?

Amy