It is currently 18 Jan 2018, 11:51

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# M21-32

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 43323

Kudos [?]: 139426 [0], given: 12790

### Show Tags

16 Sep 2014, 00:15
Expert's post
13
This post was
BOOKMARKED
00:00

Difficulty:

95% (hard)

Question Stats:

55% (02:25) correct 45% (02:58) wrong based on 75 sessions

### HideShow timer Statistics

If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars?

A. $7.00 B.$7.50
C. $8.50 D.$9.00
E. $10.00 [Reveal] Spoiler: OA _________________ Kudos [?]: 139426 [0], given: 12790 Math Expert Joined: 02 Sep 2009 Posts: 43323 Kudos [?]: 139426 [0], given: 12790 Re M21-32 [#permalink] ### Show Tags 16 Sep 2014, 00:15 Expert's post 2 This post was BOOKMARKED Official Solution: If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars? A.$7.00
B. $7.50 C.$8.50
D. $9.00 E.$10.00

Given:

$$5d+35c=7p$$, so $$c=\frac{7p-5d}{35}$$;

$$4d+4p=56c$$, so $$c=\frac{d+p}{14}$$, also if we reduce this equation by 2 we'll get: $$2d+2p=28c$$;

From above we have that $$\frac{7p-5d}{35}=\frac{d+p}{14}$$, which simplifies to $$p=\frac{5d}{3}$$.

Question:

$$p+28c=?$$ Since $$2d+2p=28c$$, then $$p+28c=p+(2d+2p)=2d+3p=2d+3*\frac{5d}{3}=7d$$.

_________________

Kudos [?]: 139426 [0], given: 12790

Intern
Joined: 17 Sep 2015
Posts: 12

Kudos [?]: 4 [2], given: 8

GMAT 1: 760 Q50 V42
GPA: 3.65

### Show Tags

15 Oct 2015, 14:09
2
KUDOS
Struggling to see how this can be done in 2 min... Bunuel, any thoughts?

Kudos [?]: 4 [2], given: 8

Manager
Joined: 17 May 2016
Posts: 67

Kudos [?]: 66 [0], given: 105

GMAT 1: 720 Q49 V39
GPA: 3.7
WE: Analyst (Investment Banking)

### Show Tags

30 May 2016, 03:23
I find it very hard to sort of discover which way to take and which variable to try to identify when it comes to questions like this. What is the logic that drives the decision to move c on one side? Any advice? many thanks!
_________________

My debrief: Self-study: How to improve from 620(Q39,V36) to 720(Q49,V39) in 25 days!

Kudos [?]: 66 [0], given: 105

Senior Manager
Joined: 18 Jan 2010
Posts: 257

Kudos [?]: 190 [1], given: 9

### Show Tags

30 May 2016, 03:53
1
KUDOS
3
This post was
BOOKMARKED
Bunuel wrote:
If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars?

A. $7.00 B.$7.50
C. $8.50 D.$9.00
E. \$10.00

Strategy in such questions is to eliminate each variable one by one.

First Form equations:

Eq. 1: 5d+35c = 7p
Eq. 2 : 4d+4p = 56c

Eliminate 1 variable
From eq 1: p = (5/7)d+5c
Put this in Eq 2:

4d+4{(5/7)d+5c} = 56 c

4d+ (20/7)d+ 20 c = 56 c

(48/7) d = 36 c
c = (4/21)d

Express p also in terms of d
p = (5/7)d+5c

p = (5/7)d+ 5 (4/21) d = (15/21) d + (20/21) d = (35/21) d = (5/3)d

Now come to the question once again: 1 pound and 28 crowns is equivalent to how many dollars?

1p+28c = (5/3)d + 28* (4/21) d = (5/3) d + (16/3) d = (21/3) d = 7 d

Kudos [?]: 190 [1], given: 9

Intern
Joined: 12 Jan 2017
Posts: 1

Kudos [?]: [0], given: 1

Location: United States
Concentration: Finance, Technology
GMAT 1: 720 Q49 V41
WE: Information Technology (Military & Defense)

### Show Tags

30 Mar 2017, 17:49
Why do you decide to solve for C first vice any of the others? Or does it matter? I tried solving for P first and it messed me up.

Kudos [?]: [0], given: 1

Manager
Joined: 23 Nov 2016
Posts: 65

Kudos [?]: 15 [0], given: 21

Location: United States (MN)
GMAT 1: 760 Q50 V42
GPA: 3.51

### Show Tags

08 Sep 2017, 21:57
Has anyone tried this with Linear Algebra? Trying to find a faster way..

Kudos [?]: 15 [0], given: 21

Senior Manager
Joined: 08 Jun 2015
Posts: 365

Kudos [?]: 27 [0], given: 106

Location: India
GMAT 1: 640 Q48 V29

### Show Tags

15 Dec 2017, 08:39
Express the facts given in the two statements as :

5D+35C=7P
4D+4P=56C

We need to find P+28C. Here D stands for dollar, C for Crown , and P for Pound.

Express P in terms of C and C in terms of D. Substitute in P+28C to get the answer as option A.
_________________

" The few , the fearless "

Kudos [?]: 27 [0], given: 106

Intern
Joined: 06 Jul 2015
Posts: 26

Kudos [?]: 5 [0], given: 9

### Show Tags

15 Dec 2017, 18:50
I don't know if this is a subtle approach or not; 5,35,7 ,35 is divisible by 7 and 5; 4,4,56 , 56 is divisible by 4 ; 1,28? any number that divides 28, the only number that divides 28 is 7;

Kudos [?]: 5 [0], given: 9

Re: M21-32   [#permalink] 15 Dec 2017, 18:50
Display posts from previous: Sort by

# M21-32

Moderators: chetan2u, Bunuel

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.