Breakdown of Учёные спорят о радиусе и экваторе приблизительно в ста девяноста странах.
и
and
в
in / to (direction)
о
about (о, об, обо)
спорить
to argue
Questions & Answers about Учёные спорят о радиусе и экваторе приблизительно в ста девяноста странах.
How does the declension of сто девяносто work in this sentence?
It is in the prepositional case, matching странах (countries), because of the preposition в. When declining compound numbers, every word in the number must change its case. Here, both сто and девяносто change to their prepositional forms: ста and девяноста.
Why do both ста and девяноста end in -а for the prepositional case? Shouldn't prepositional endings usually be -е?
The numbers 40, 90, and 100 belong to a special group. They only have two forms: the nominative/accusative form (сорок, девяносто, сто) and a single form for all other oblique cases, which always ends in -а (сорока, девяноста, ста). Since this sentence requires the prepositional case, both parts take their -а ending.
Why is the preposition в placed after приблизительно? Could I say в приблизительно ста девяноста странах?
It is much better Russian to keep the preposition в directly next to the word it governs (the number ста). While you might hear native speakers occasionally put the preposition before adverbs like приблизительно in casual speech, standard Russian strongly prefers приблизительно в ста девяноста странах.
Why does the noun учёные have an adjective ending?