Question

The sequence below shows Marisa’s library fine starting on the first day her book is overdue and for each additional day afterward:

$0.50, $0.65, $0.80, $0.95, $1.10, ...

Let f(n) represent Marisa’s library fine (in dollars), where n is the number of days the book has been overdue, starting with n=1 for the first day overdue.

Which equation represents Marisa’s library fine as a function of a book that is n days overdue?

Answer 1

The amounts increase by $0.15 each day, so f(n) is an arithmetic sequence with first term $0.50:

f(n) = 0.50 + 0.15(n − 1) = 0.15n + 0.35, for n = 1, 2, 3, ...