A certain library assesses fines for overdue books as

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BTGmoderatorLU: Moderator; Posts: 2544; Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members

by BTGmoderatorLU » Sat Jan 26, 2019 7:42 pm

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Source: GMAT Prep

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 each 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 for a book on the fourth day it is overdue?

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

The OA is B

Source: Beat The GMAT — Problem Solving | Sat Jan 26, 2019 7:42 pm

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by GMATGuruNY » Sun Jan 27, 2019 3:07 am

BTGmoderatorLU wrote:Source: GMAT Prep

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 each 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 for a book on the fourth 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.

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by Brent@GMATPrepNow » Sun Jan 27, 2019 4:49 am

BTGmoderatorLU wrote:Source: GMAT Prep

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 each 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 for a book on the fourth day it is overdue?

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

The OA is B

1st day - $0.10

2nd day - $0.20 or $0.40 (double or add $0.30)
$0.20 is the lesser amount

3rd day - $0.40 or $0.50 (double or add $0.30)
$0.40 is the lesser amount

4th day - $0.80 or $0.70 (double or add $0.30)
$0.70 is the lesser amount

The correct answer is B

Cheers,
Brent

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by [email protected] » Sun Jan 27, 2019 12:32 pm

Hi ALL,

This question includes a 'conditional statement' that effects how you're supposed to handle each "step" in the math:

"for each additional day....., the total fine is EITHER increased by 30 cents OR doubled, whichever results in the LESSER AMOUNT."

Since we're asked to calculate a book that is 4 days overdue, we just have to consider each possible outcome on each day, then choose the one that leads to the "lesser amount"

Day 1: 10 cents

Day 2: 10 + 30 = 40 cents; 10(2) = 20 cents
20 cents is LOWER, so the fine is NOW 20 cents

Day 3: 20 + 30 = 50 cents; 20(2) = 40 cents
40 cents is LOWER, so the fine is NOW 40 cents

Day 4: 40 + 30 = 70 cents; 40(2) = 80 cents
70 cents is LOWER, so the final fine is 70 cents.

Final Answer: B

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by Scott@TargetTestPrep » Wed Jan 30, 2019 6:03 pm

BTGmoderatorLU wrote:Source: GMAT Prep

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 each 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 for a book on the fourth day it is overdue?

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

The OA is B

On day 1, the fine is $0.10.

On day 2, we have two options:

1) 0.10 + 0.30 = $0.40

2) 0.10 x 2 = $0.20

Since option 2 is the lesser of the 2 fines, the total fine, as of day 2, is $0.20.

On day 3 we have two options:

1) 0.20 + 0.30 = $0.50

2) 0.20 x 2 = $0.40

Since option 2 is the lesser of the 2 fines, the total fine, as of day 3, is $0.40.

On day 4 we have two options:

1) 0.40 + 0.30 = $0.70

2) 0.40 x 2 = $0.80

Since option 1 is the lesser of the 2 fines, the total fine, as of day 4, is $0.70.

Answer: B

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