Don't understand this problem (seems easy)

[H2O]

Hi all,

I encountered the following problem on the practice GMAT and for some reason can't figure out why they got the answer they did.

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

Seems easy, but I keep getting the wrong answer. Maybe I'm not reading it right.

[punit.kaur.mba]

My answer is 0.7. Whats the OA?

[H2O]

My answer was $0.90, but the correct answer is $0.70, what you got. Can you please explain?

[punit.kaur.mba]

ok here you go:

1st day - 0.1
2nd day - either 0.4(0.1+0.3) or 0.2(0.1 x 2) . We choose the least so 0.2
3rd day - either 0.5(0.2 + 0.3) or 0.4(0.2 x 2). We choose 0.4
4th day - either 0.7(0.4 + 0.3) or 0.8(0.4 x 2). We choose 0.7

Ans is 0.7

Let me know if u have quest.

[H2O]

Oh, I see, I was not reading the problem right. When it said "the total amount" I thought I had to add the amount from the previous day to the next day and double or add .30 to that number. This was confusing. Thank you for explaining.