Breakdown of Мы говорили о семистах граммах мяса в этом блюде.
мы
we
этот
this [f: эта, n: это]
говорить
to speak, to talk
в
in / to (direction)
Questions & Answers about Мы говорили о семистах граммах мяса в этом блюде.
How is the word семистах formed here?
This is the prepositional case of семьсот (seven hundred), triggered by the preposition о (about). When declining hundreds, both halves of the word change. The first part declines like the number seven (семь becomes семи), and the second part (сот) becomes стах in the prepositional case. Together, they make семистах.
Numbers usually force the following noun into the genitive case. Why is it граммах (prepositional plural) instead of граммов?
That genitive rule only applies when the number is in the nominative or inanimate accusative case! In all other cases (the oblique cases), the number and the noun agree in case. Because the preposition о forces the number into the prepositional case (семистах), the noun it counts must also be in the prepositional plural (граммах).
Why doesn't мяса also match the prepositional case of семистах граммах?
Because the number is counting the grams, not the meat directly. The phrase translates to '700 grams of meat'. No matter what case the '700 grams' block is in, the word for 'of meat' will remain in the genitive case (мяса).
Why do we use о here instead of об?