In these areas (subject-verb agreement), there are actually three 'rules' or principles which operate: grammatical concord, notional concord (or synesis), and the proximity principle. Which one takes precedence is not set in tablets of stone.
For instance, both US and UK usage would require The team was founded in 1922. This is grammatical concord - the singular verb form agreeing with the singular noun.
However, The team has been training every day for the last two months would similarly be used in the US, while in the UK The team have been training every day for the last two months would be far more usual. This (UK) usage is called notional concord: the individual team members are implied, and the concord reflects this. Notional concord is often used with constructions using collective nouns (from the mundane - group, staff, family - to the esoteric - a gaggle of geese were approaching) and quantifiers. I'd always say:
There are many companies... (as would we all!);
There are a large number of companies...
There are a / one hundred companies... (nice example, Jeff).
Also, 25% / 1/4 of companies are ... (but 1/4 is less than 1/3)
For completeness, I'll add a quote from CS Lewis on the accepted use of the proximity principle when the (other) 'rules' would argue against such usage:
"Don't take any notice of teachers and text-books in such matters. Nor of logic. It is good to say 'More than one passenger was hurt,' although more than one equals at least two and therefore logically the verb ought to be plural were not singular was!"
(C.S. Lewis, letter to Joan, June 26, 1956. C. S. Lewis' Letters to Children, ed. by Lyle W. Dorsett and Marjorie Lamp Mead. Touchstone, 1995)
And the 'rules' sometimes don't even suggest 'the right answer':
"Sometimes syntax itself makes it impossible to follow the agreement rule. In a sentence like Either John or his brothers are bringing the dessert, the verb can't agree with both parts of the subject. Some people believe that the verb should agree with the closer of the two subjects. This is called agreement by proximity."
(The American Heritage Book of English Usage. Houghton Mifflin, 1996)
It is usually best to check with say style guides approved by the people paying for the writing.
There aren't universal rules in English - no-one would replace the ill-formed "It's us" with
"It are us"
"They are us"
"It are we" ...
And in the US, apparently The Beatles were and the Stones were reflect UK usage, as does Jethro Tull was (the band!), but Metallica was doesn't!