NUMBER, GRAMMATICAL

See Collectives as Singular or Plural, FRACTIONS, none, and Plurals.

Generally speaking, a number or measurement is singular if considered as a mass:

            nine gallons is enough

            300 miles was a lot to drive in a day

and plural if considered as separate units:

            10 dishfuls were slowly doled out

The object of a preposition following a fraction or percentage usually governs the verb:

            Half the wine is enjoyed ...

            Half these people are engaged ...

            Two-thirds of humanity lives ...

            35 percent of the bread goes ...

            35 percent of the grapes go ...