I answered my own question this seems to be an exception to the rules. Below is taken from the MGMAT guide:
In many idiomatic expressions that designate qyantities or ~ such as a number of, the
subject of the sentence is in an Ofprepositional phrase. These expressions provide the exception
to the rule that the subject cannot be in a prepositional phrase. We have seen the
SANAM pronouns as examples of this phenomenon. Other examples include fractions and
percents:
Half of the is blueberry, and half of the are already gone.
The words majority, minority, and plurality are either singular or plural, depending on their
context. If you want to indicate the many individual parts of the totality, use a plural verb.
If you want to indicate the totality itself then use a singular verb form.
The majority of the stydents in this class ABE hard workers.
In the Senate, the majority HAS coalesced into a unified voting block.
Treat quantity phrases in the same way as SANAM pronouns: the noun in the Of prepositional
phrase will indicate whether the verb is singular or plural.
