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A number of questions “has been” or “have been” asked?
From the grammatical view both are correct, but please explain the difference in meaning:
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The number of students in the class is fifteen.
The verb is singular because it refers to 'the number'. The subject of this sentence is 'the number'. 'Of students' is a modifier of 'the number'
'A number of' means several, some.
Several students were late for class.
Some students were late for class.
A number of students were late for class.
The subject of these sentences is 'students', and 'some', 'several', 'a number of' are modifiers of 'students'. The verb agrees with the subject.
It has to do with the definiteness or indefiniteness of the number.
1 - The number of students in the class IS fifteen. <-a definite number (15)
2 - A number of students WERE late for class. <-an indefinite number (?)
In (1) the number of students is definitely known to be 15, a particular number. So we use the definite article, and the singular verb.
In (2) the number of students late to class is unknown or unspecified. So we use the indefinite article, and the plural verb.
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The first sentence informs you about the number which is singular
The number is fifteen
The second one is about the students which is plural word
Students were late
