Problem Solving

A certain library assesses fines for overdue books as follows. On the first day that a book is overdue, the total fine is $0.10. For reach additional day that the book is overdue, the total fine is either increased by $0.30 or doubled, whichever results in the lesser amount. What is the total fine for a book on the 4th day it is overdue?

A) $0.60
B) $0.70
C) $0.80
D) $0.90
E) $1.00

First day:
Total fine = 10.

For each additional day, the total fine either increases by 30 or doubles -- whichever results in a lesser amount.

Second day:
Adding 30 cents to the 1-day fine, we get 10+30 = 40.
Doubling the 1-day fine, we get 2*10 = 20.
Total fine = lesser amount = 20.

Third day:
Adding 30 cents to the 2-day fine, we get 20+30 = 50.
Doubling the 2-day fine, we get 2*20 = 40.
Total fine = lesser amount = 40.

Fourth day:
Adding 30 cents to the 3-day fine, we get 40+30 = 70.
Doubling the 3-day fine, we get 2*40 = 80.
Total fine = lesser amount = 70.

The correct answer is B.

Rule : increase by 0.30 or double.. which ever is less

Total Fine on First Day : 0.10
Total Fine on Second Day : 0.20
Total Fine on third Day : 0.40
Total Fine on Forth Day : 0.70
Answer [spoiler]{B}[/spoiler]