If the object of the preposition is singular, use a singular verb. If the object of the preposition is plural, use a plural verb. Examples Fifty percent of the pie has disappeared . Pie is the object of the preposition of . Fifty percent of the pies have disappeared.
Pies is the object of the preposition.
One third of the city is unemployed. One third of the people are unemployed. All of the pie is gone. All of the pies are gone. Some of the pie is missing .