In the "Singular or Plural" test on this site I have found two questions to be very confusing. Q10 - 'A number of is followed by a _______verb' (Ans. Plural) & Q11 - 'The number of' is followed by a _______ verb' (Ans. Singular).
What is the difference, I still havent been able to figure this one out!
A number of people are going to see that report.
"The number of" is eventually followed by an actual number or by a descriptive term. In either case it takes a singular verb, usually "is".
The number of people going to see that report is (five)(small)(unknown).
The above is a short summary, and there may be some exceptions.