In 60% of the 77 coasts investigated, it is understood that there is a possibility that all the sand will be lost.
I'm a bit confused by the 調べた７７の海岸のうち６０％で part. I'm assuming it means "in 60% of the 77 coasts investigated", but I'm uncomfortable with the lack of particle between うち and 60%. How do the following differ:
７７の海岸のうちの６０％で this one feels ungrammatical to me
Maybe I'm trying to join ７７の海岸のうち and 60% into a single phrase when I shouldn't. Perhaps the correct answer is "Among the 77 coasts investigated, in 60% of them ...". Could I write ７７の海岸のうち、それの６０％で with the same meaning as the original?