bmwhype2
A variety of gold coins were/was stolen from the vault.
It's hard to say. When you say - A VARIETY OF GOLD COINS WAS STOLEN - it could mean A SPECIFIC Variety was stolen as opposed to the intended meaning of a number of gold coins having been stolen.
In the other meaning - when by VARIETY we mean a number of different kinds of gold coins - we definitely need the WERE for SVA.
If we get something like this on the GMAT - I would just trust my gut instinct and pick up - were, because sometimes the SVA is ascertained by the OBJECT of preposition OF - so since coins is plural we must have a plural verb.
However, this rule (where the verb is determined by the plurality of the object of preposition OF) holds when OF is preceded by one of the SANAM pronouns (Some, all, None, Any, Most)
Some of the coins WERE lost
None of the paintings WERE mine
Some of the dough WAS stolen