[Basic Japanese] だれの questions

[myonashiro]

I was checking my answers at Genki I and I wrote for the sentence "Whose cap is this?"
My translation: この帽子はだれのですか。
Book's answer: これはだれの帽子ですか。

Is my translation incorrect or both ways are correct?

 

[Toritoribe]

Speaking strictly, your translation means "Whose one is this cap?" What the two questions are asking are the same, though.

 

[myonashiro]

Thank you!