GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Nov 2019, 01:23

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Trickster Rabbit agrees with Foolish Fox to double Fox's money every

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59210
Trickster Rabbit agrees with Foolish Fox to double Fox's money every  [#permalink]

Show Tags

New post 25 Apr 2019, 03:44
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

74% (02:03) correct 26% (02:11) wrong based on 35 sessions

HideShow timer Statistics

Trickster Rabbit agrees with Foolish Fox to double Fox's money every time Fox crosses the bridge by Rabbit's house, as long as Fox pays 40 coins in toll to Rabbit after each crossing. The payment is made after the doubling, Fox is excited about his good fortune until he discovers that all his money is gone after crossing the bridge three times. How many coins did Fox have at the beginning?

(A) 20
(B) 30
(C) 35
(D) 40
(E) 45

_________________
GMAT Club Legend
GMAT Club Legend
User avatar
V
Joined: 12 Sep 2015
Posts: 4074
Location: Canada
Re: Trickster Rabbit agrees with Foolish Fox to double Fox's money every  [#permalink]

Show Tags

New post 25 Apr 2019, 08:18
1
Top Contributor
Bunuel wrote:
Trickster Rabbit agrees with Foolish Fox to double Fox's money every time Fox crosses the bridge by Rabbit's house, as long as Fox pays 40 coins in toll to Rabbit after each crossing. The payment is made after the doubling, Fox is excited about his good fortune until he discovers that all his money is gone after crossing the bridge three times. How many coins did Fox have at the beginning?

(A) 20
(B) 30
(C) 35
(D) 40
(E) 45


Let's test the answer choices.

We know that the answer can't be A (20), because the game would be over after Fox crosses the bridge ONCE.

So, let's start with B (30)
Fox starts with 30 coins
1st bridge crossing: double coins to have 60 coins. Pay 40 coins. 20 coins remaining.
2nd bridge crossing: double coins to have 40 coins. Pay 40 coins. 0 coins remaining.
GAME OVER.
Fox is supposed to cross THREE times.
Eliminate B

Test C (35)
Fox starts with 35 coins
1st bridge crossing: double coins to have 70 coins. Pay 40 coins. 30 coins remaining.
2nd bridge crossing: double coins to have 60 coins. Pay 40 coins. 20 coins remaining.
3rd bridge crossing: double coins to have 40 coins. Pay 40 coins. 0 coins remaining.
PERFECT! Fox crossed exactly THREE times.

Answer: C

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Image
GMAT Tutor
avatar
G
Joined: 24 Jun 2008
Posts: 1827
Re: Trickster Rabbit agrees with Foolish Fox to double Fox's money every  [#permalink]

Show Tags

New post 25 Apr 2019, 09:13
We can also work forward. If the fox starts with f coins, then crossing the bridge once leaves him with 2f - 40 coins, crossing twice leaves him with 2(2f-40) - 40 coins, and crossing a final time leaves him with 2[2(2f-40) - 40] - 40 coins. We know that's equal to zero:

2[2(2f-40) - 40] - 40 = 0 --> we can factor a '2' from within the square brackets
4[(2f - 40) - 20] - 40 = 0 --> we can now divide both sides by 4
2f - 40 - 20 - 10 = 0 --> get the numbers on the right
2f = 70
f = 35

Of course there are lots of other ways to complete the solution to this equation.
_________________
GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com
GMAT Club Bot
Re: Trickster Rabbit agrees with Foolish Fox to double Fox's money every   [#permalink] 25 Apr 2019, 09:13
Display posts from previous: Sort by

Trickster Rabbit agrees with Foolish Fox to double Fox's money every

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne