I'm studying for an actuarial exam and it always confuses me when I'm trying to count intervals in annuities.
For example, if I want to know how many payment periods there are from period 13 to period 27, what is the length of this interval?
A more general example of my problem would be to count the numbers between 99 and 56.
What are some general tips when doing this sort of counting? P.S. sorry I don't know the proper tags for this question.
This is not a pure mathematical question. Depends on the exact meaning of words "between ... and" and "from .. to". 2nd question is tricky ... if order is important, then no number is between 99 and 56.