It is now 47 years since I obtained my First in Mathematics and I have obviously been interested in the posting responses to the original query, which was an "old chestnut" when I first attended grammar school in the 1955/1956 school term. All I will say that a few of those postings have answered the query correctly in a clear and logical manner and I was amused to read of the computer usage, as this was a subject area that did not even exist outside certain development bodies when I was studying this subject.
May I, with my mathematical pedantic hat on, give those younger forum members still in secondary education another mathematical conundrum to ponder upon. If, during the theoretical discussions on calculus, bring the matter of infinity into the discussions. My contention is that infinity is not a number for the vast number of mathematical possibilities but there are still certain scenarios where infinity in calculus can behave like a number.