[Grammar] singular or plural? So confusing...

[norae99]

Hi, I have some questions about singular or plural forms of verbs in the sentences below.

1) More than three-fourths of the population between the ages of five and nineteen [ is / are ] now enrolled.

2) Nearly three tons of rice [ was / were ] dumped in the ocean.

3) Parts of the theory [ seems / seem ] impossible to believe.

They are so confusing......Please help me...

Thank you in advance.

 

[tedtmc]

not a teacher

more than three quarter - countable and finite - are
three tons of rice - uncountable - was
parts of the theory - plural - are