|See Collectives as Singular or Plural, FRACTIONS, none, and Plurals.
Generally speaking, a number or measurement is singular if considered as
ten gallons is enough
300 miles was a lot to drive in a day
and plural if considered as separate units:
ten dishfuls were slowly
The object of a preposition following a fraction or percentage usually governs the verb:
Half the wine is enjoyed ...
Half of these people are engaged ...
Two-thirds of humanity lives ...
35 percent of the bread goes ...
35 percent of the grapes go ...