It is currently 18 Oct 2017, 06:42

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A jewel necklace contains only emeralds, rubies, and diamonds. If the

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 128713 [0], given: 12182

A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 01:56
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

74% (00:56) correct 26% (01:53) wrong based on 43 sessions

HideShow timer Statistics

A jewel necklace contains only emeralds, rubies, and diamonds. If the ratio of emeralds to diamonds is 2:7 and the ratio of diamonds to rubies is 3:2, then which of the following could not be the number of jewels on the necklace?

(A) 41

(B) 81

(C) 82

(D) 123

(E) 205
[Reveal] Spoiler: OA

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 128713 [0], given: 12182

1 KUDOS received
Manager
Manager
avatar
B
Joined: 21 Feb 2017
Posts: 86

Kudos [?]: 3 [1], given: 23

GMAT ToolKit User
Re: A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 02:00
1
This post received
KUDOS
B.
Rest all are multiple of 41 and ratio of e:d:r marble is 6:21:14. Add 6+21+14=41.


Sent from my XT1663 using GMAT Club Forum mobile app

Kudos [?]: 3 [1], given: 23

Intern
Intern
User avatar
Joined: 28 May 2017
Posts: 18

Kudos [?]: 4 [0], given: 0

Re: A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 02:06
B -81 is the answer

Coz after simplifying
Emeralds : diamond : rubies

6 : 21: 14

So total 41 so every option that is divisible by 41 can be the no of jewels

So the only no not divisible by 41 is 81

So 81 is the answer B


Sent from my iPhone using GMAT Club Forum

Kudos [?]: 4 [0], given: 0

Director
Director
avatar
P
Joined: 22 May 2016
Posts: 806

Kudos [?]: 258 [0], given: 546

A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 13:06
DOUBLE POST, SEE BELOW

Last edited by genxer123 on 16 Aug 2017, 13:17, edited 1 time in total.

Kudos [?]: 258 [0], given: 546

Director
Director
avatar
P
Joined: 22 May 2016
Posts: 806

Kudos [?]: 258 [0], given: 546

Re: A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 13:13
genxer123 wrote:
Bunuel wrote:
A jewel necklace contains only emeralds, rubies, and diamonds. If the ratio of emeralds to diamonds is 2:7 and the ratio of diamonds to rubies is 3:2, then which of the following could not be the number of jewels on the necklace?

(A) 41

(B) 81

(C) 82

(D) 123

(E) 205

Emeralds : Diamonds = 2:7 and
Diamonds : Rubies = 3:2

Before you can figure out how many total jewels might be on a necklace, you have to know the relationship among emeralds and diamonds and rubies.

But because the ratio number for diamonds doesn't match, you can't figure out that relationship until you make a common term.

The method is derivable, but maybe just writing it out will help.

There are two ratios that share a common element , diamonds. To find the combined relationship, find the equivalent of the least common multiple.

That is, figure out how to make diamonds equal in both ratios, and then you can combine ratios .

1. Write the ratios as you have them, putting the element they have in common in the middle

|__E__|__D__|__R__|
|__2__|__7__|-------|
|-------|__3__|__2__|

2. You need the Ds (diamonds) to be equal. Take the LCM of 3 and 7 = 21.

3. Then multiply each row by the number that will get you to D = 21: multiply both parts of the first row by 3, and both parts of the second row by 7

|__E__|__D__|__R__|---------------->|__E__|__D__|__R__|
|__2__|__7__|-------| ---- x 3------->|__6__|__21__|--------|
|-------|__3__|__2__| ---- x 7------->|--------|__21__|__14__|

The right hand chart shows the combined ratio where E: D: R = 6x: 21x: 14x

Total parts of combined ratio: 6x + 21x + 14x = 41x

So the answer has to be a multiple of 41.

81 is not a multiple of 41.

Answer B


P.S. If you're on a phone, turn it to landscape. Then the charts will line up. (Wow is it hard to make charts . . . .)

Kudos [?]: 258 [0], given: 546

BSchool Forum Moderator
User avatar
P
Joined: 26 Feb 2016
Posts: 1450

Kudos [?]: 593 [0], given: 16

Location: India
Concentration: General Management, Leadership
WE: Sales (Retail)
Premium Member CAT Tests
Re: A jewel necklace contains only emeralds, rubies, and diamonds. If the [#permalink]

Show Tags

New post 16 Aug 2017, 20:17
Let the emeralds in the necklace be represented by E,
the rubies in the necklace be represented by R and diamonds in the necklace by D.
Therefore,
E:D = 2x:7x
D:R = 3x:2x

Since we need to find a common ratio, we need to multiply the emerald, diamond ratio by a factor of 3 and the diamond, ruby ratio by a factor of 7.
E:D also equals 6x : 21x and D:R equals 21x : 14x
Hence, the common ratio is 6x : 21x : 14x.

Therefore, the total number of jewels in the necklace is a mutliple of 41(6x + 21x +14x = 41x)
Of the answer options(Only B, 81) is not a multiple of 41 and is our answer.
_________________

Stay hungry, Stay foolish

2017-2018 MBA Deadlines

Class of 2020: Rotman Thread | Schulich Thread
Class of 2019: Sauder Thread

Kudos [?]: 593 [0], given: 16

Re: A jewel necklace contains only emeralds, rubies, and diamonds. If the   [#permalink] 16 Aug 2017, 20:17
Display posts from previous: Sort by

A jewel necklace contains only emeralds, rubies, and diamonds. If the

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


cron

GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.