Adjektivendungen mit Genitiv und Indefinitpronomen für eine unbestimmte Anzahl

Question

Wessen grün_ Mantel ist das? Er ist Besitzer vieler teur_ Autos (Genitiv).

I‘m trying to solve some exercises on Adjektivendungen and I‘m facing difficulty understanding these two parts. The answers of the book are:

grüner und teurer

Whereas I thought the answers should be -en und -en.

Could you please explain to me why the endings are -er? Thanks :)

Answer 1

1. Wessen? is a question word which is followed be the nominative case, and expects an answer in the genitive case.

You need the strong declension without articles.

Ein grüner Mantel. -> Wessen grüner Mantel? -> [Der grüne Mantel]₁ [der Frau]₂.

₁Nominative, definite article
₂Genitive

Or in the plural case

Wessen grüne Mäntel? -> Die grünen Mäntel der Frau.

Viel ist actually a special case, which is quite complicated and even confused me as a native speaker.

You can treat it as an indefinite amount (Numerale indefinitum), which then requires the mixed declension plural genitive form.

Er ist Besitzer vieler teuren Autos

Or you can treat it as a fellow adjective, so both adjective will be in the strong plural genitive case

Er ist Besitzer vieler teurer Autos

similar to

Er ist Besitzer schneller teurer Autos