GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 18 Jan 2020, 09:43

### 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

# Marty has a coin collection, which consists of only New World and Old

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 60468
Marty has a coin collection, which consists of only New World and Old  [#permalink]

### Show Tags

16 Aug 2017, 01:59
1
1
00:00

Difficulty:

15% (low)

Question Stats:

84% (02:13) correct 16% (02:21) wrong based on 68 sessions

### HideShow timer Statistics

Marty has a coin collection, which consists of only New World and Old World coins, in a ratio of 3:1. Marty’s friend Kyle swaps 28 of his Old World Coins for 28 of Martin’s New World coins. If Marty now has as many Old World coins as he does New World coins, how many coins did Marty originally have in his collection?

(A) 28

(B) 84

(C) 112

(D) 130

(E) 390

_________________
Manager
Joined: 06 Jul 2014
Posts: 87
Location: India
Concentration: Finance, Entrepreneurship
GMAT 1: 660 Q48 V32
Re: Marty has a coin collection, which consists of only New World and Old  [#permalink]

### Show Tags

16 Aug 2017, 02:12
1
3x-28/x+28=1; 2x=56; x=28; 4x=112
Intern
Joined: 22 Apr 2015
Posts: 25
WE: Business Development (Internet and New Media)
Re: Marty has a coin collection, which consists of only New World and Old  [#permalink]

### Show Tags

16 Aug 2017, 04:39
2
$$\frac{Nw}{Ow}$$=3=> Nw= 3Ow

After the swap
Nw-28= Ow+28
=>3 Ow-28= Ow+28
=>2Ow= 56
=>Ow= 28
Nw=3ow= 28*3= 84

Total coins originally = 84+28=112

Ans- C
Intern
Joined: 30 May 2017
Posts: 7
Marty has a coin collection, which consists of only New World and Old  [#permalink]

### Show Tags

16 Aug 2017, 05:47
Old Ratio (New Coins:Old Coins) : 3:1
Total Coins = 3n + n = 4n

New Ratio: 1:1
New Arrange: (3n-28 / n+28) = (1/1)

Cross Multiply:
3n-28=n+28
2n = 56
n = 28

So, 4n = 112
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 15933
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Marty has a coin collection, which consists of only New World and Old  [#permalink]

### Show Tags

08 Dec 2019, 15:39
Hi All,

We're told that Marty has a coin collection, which consists of only New World and Old World coins, in a ratio of 3:1. Marty's friend Kyle swaps 28 of his Old World Coins for 28 Marty's New World Coins and then Marty now has as many Old World Coins as he does New World Coins. We're asked for the total number of coins that Marty originally had in his collection. Since we're dealing with ratios, this question can be solved in a number of different ways, including by TESTing THE ANSWERS.

To start, since the original ratio of New to Old coins was 3:1, this means that Marty's TOTAL COINS has to be a MULTIPLE of 4. Depending on how quickly you can do division, you'll notice that neither Answer D nor Answer E is a multiple of 4, so both of those answers can be eliminated. Let's TEST Answer B first....

IF... Marty started off with 84 coins, with a ratio of 3:1, then he had 63 New coins and 21 Old coins
by 'swapping' 28 New coins for 28 Old coins, Marty would then have 35 New coins and 49 Old coins
This is NOT a match for what we were told though (Marty is supposed to have the SAME number of each). Since we're going to swap 28 coins no matter what, we need Marty to have MORE New coins at the start...

IF... Marty started off with 112 coins, with a ratio of 3:1, then he had 84 New coins and 28 Old coins
by 'swapping' 28 New coins for 28 Old coins, Marty would then have 56 New coins and 56 Old coins
Here, Marty has the SAME number of New and Old coins, so this MUST be the answer!

GMAT assassins aren't born, they're made,
Rich
_________________
Contact Rich at: Rich.C@empowergmat.com

The Course Used By GMAT Club Moderators To Earn 750+

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Re: Marty has a coin collection, which consists of only New World and Old   [#permalink] 08 Dec 2019, 15:39
Display posts from previous: Sort by