translating question

Latin Learning Latin
1

Fundus optimus jugerum CCXL esse putabatur.

The 240 acre farm is thought to be the best.

Is jugerum singular in order to match the singular subject, fundus? Is jugerum a predicate adjective? Since jugerum is singular I thought of how people will say that a person is 6 foot tall rather than 6 feet tall.

2

Fundus optimus is the subject of putabatur. iūgerūm is a neuter noun, genitive plural. So I would take it as a partitive genitive. (See Gildersleeve 370. The Partitive genitive is used with numerals.)