Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 24 Oct 2014, 12:44

### 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

# Events & Promotions

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

# Two alloys A and B are composed of two basic elements. The

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 15 Apr 2012
Posts: 94
Location: Bangladesh
Concentration: Technology, Entrepreneurship
GMAT 1: 460 Q38 V17
GMAT 2: Q V
GPA: 3.56
Followers: 0

Kudos [?]: 14 [0], given: 134

Two alloys A and B are composed of two basic elements. The [#permalink]  30 Jun 2012, 20:15
12
This post was
BOOKMARKED
00:00

Difficulty:

75% (hard)

Question Stats:

56% (03:09) correct 44% (02:03) wrong based on 160 sessions
Two alloys A and B are composed of two basic elements. The ratios of the compositions of the two basic elements in the two alloys are 5 : 3 and 1 : 2, respectively. A new alloy X is formed by mixing the two alloys A and B in the ratio 4 : 3. What is the ratio of the composition of the two basic elements in alloy X ?

(A) 1 : 1
(B) 2 : 3
(C) 5 : 2
(D) 4 : 3
(E) 7 : 9
[Reveal] Spoiler: OA
Senior Manager
Joined: 28 Mar 2012
Posts: 286
Concentration: Entrepreneurship
GMAT 1: 640 Q50 V26
GMAT 2: 660 Q50 V28
GMAT 3: 730 Q50 V38
Followers: 15

Kudos [?]: 174 [0], given: 23

Re: Two alloys A and B [#permalink]  01 Jul 2012, 00:33
farukqmul wrote:
Two alloys A and B are composed of two basic elements. The ratios of the compositions of the two
basic elements in the two alloys are 5 : 3 and 1 : 2, respectively. A new alloy X is formed by mixing
the two alloys A and B in the ratio 4 : 3. What is the ratio of the composition of the two basic elements
in alloy X ?

(A) 1 : 1
(B) 2 : 3
(C) 5 : 2
(D) 4 : 3
(E) 7 : 9

Hi,

Proportion of 1st element in A = 5/8
Proportion of 1st element in B = 1/3
let, the proportion of 1st element in mixture = x
using allegations:
Attachment:

all.jpg [ 7.83 KiB | Viewed 6131 times ]

\frac {x-1/3}{5/8-x}= \frac 43
on solving, x=0.5
thus, proportion of two elements in the mixture is 1:1

Answer (A)

Regards,
_________________

My posts: Solving Inequalities, Solving Simultaneous equations, Divisibility Rules

My story: 640 What a blunder!

Vocabulary resource: EdPrep

Facebook page: fb.com/EdPrep

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 4877
Location: Pune, India
Followers: 1156

Kudos [?]: 5378 [3] , given: 165

Re: Two alloys A and B are composed of two basic elements. The [#permalink]  15 Aug 2012, 04:36
3
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
farukqmul wrote:
Two alloys A and B are composed of two basic elements. The ratios of the compositions of the two basic elements in the two alloys are 5 : 3 and 1 : 2, respectively. A new alloy X is formed by mixing the two alloys A and B in the ratio 4 : 3. What is the ratio of the composition of the two basic elements in alloy X ?

(A) 1 : 1
(B) 2 : 3
(C) 5 : 2
(D) 4 : 3
(E) 7 : 9

Responding to a pm:

When you need to find the average, it is better to use the formula in its original form: Avg = (C1*w1 + C2*w2)/(w1 + w2)
Avg = [(5/8)*4 + (1/3)*3]/(4+3) = 1/2
Ratio of the 2 elements in the mixture = 1:1

Obviously the formula will work in the other form too though it is best to use that when you need to find the ratio of the weights. Using the formula in the other form: w1/w2 = (A2 - Aavg)/(Aavg - A1)
element 1 in A = 5/8
element 1 in B = 1/3
element 1 in mixture = x

4/3 = (1/3 - x) / (x - 5/8)
4/3(x - 5/8) = 1/3 - x
(7/3)x = 7/6
x = 1/2
(You made a calculation error)

Ratio of elements in the mixture = 1:1
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Save $100 on Veritas Prep GMAT Courses And Admissions Consulting Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options. Veritas Prep Reviews Director Joined: 22 Mar 2011 Posts: 612 WE: Science (Education) Followers: 73 Kudos [?]: 529 [4] , given: 43 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 15 Aug 2012, 05:00 4 This post received KUDOS farukqmul wrote: Two alloys A and B are composed of two basic elements. The ratios of the compositions of the two basic elements in the two alloys are 5 : 3 and 1 : 2, respectively. A new alloy X is formed by mixing the two alloys A and B in the ratio 4 : 3. What is the ratio of the composition of the two basic elements in alloy X ? (A) 1 : 1 (B) 2 : 3 (C) 5 : 2 (D) 4 : 3 (E) 7 : 9 Mixture A has a total of 5 + 3 = 8 parts. If in the final mixture this represents 4 parts, then the total number of parts in mixture B should be (8/4)*3 = 6. So, we should take of mixture B a quantity with 2 and 4 parts, respectively. This will give us in the final mixture (5 + 2) : (3 + 4), which means 7:7, or 1:1. Answer A. _________________ PhD in Applied Mathematics Love GMAT Quant questions and running. Intern Joined: 19 Feb 2012 Posts: 25 Location: India Concentration: Technology, General Management Schools: WBS '15 GMAT 1: 700 Q48 V38 GPA: 3.36 WE: Analyst (Computer Software) Followers: 0 Kudos [?]: 5 [0], given: 7 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 29 Oct 2012, 01:48 Alloy A: Since F:S = 5:3, and 5+3=8, F/total = 5/8. Alloy B: Since F:S = 1:2, and 1+2 = 3, F/total = 1/3. Mixture T: A:B = 4:3. If we mix 8 units of A with 6 units of B, we get: Amount of F in alloy A = (5/8)8 = 5 units Amount of F in alloy B = (1/3)6 = 2 units. (Total F)/(Mixture T) = (5+2)/(8+6) = 7/14 = 1/2. Since 1/2 of the mixture is composed of F, F:S = 1:1. Intern Joined: 31 Oct 2012 Posts: 24 Followers: 0 Kudos [?]: 1 [0], given: 4 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 15 Dec 2012, 21:30 Ratio of Elements A - 5:3 / 5x:3x B - 1:2 / 1y:2y Ratio of Alloys A+B - 4:3 ie. A:B = 4:3 (5x+3x):(1y+2y) = 4:3 8x:3y = 4:3 x:y = 1:2 => y = 2x Ratio of elements in (A+B) 1st element in A and B / 2nd Element in A and B (5x + y)/(3x + 2y) but y = 2x ie. 7x/7x = 1:1 Ans A Intern Joined: 24 Apr 2012 Posts: 48 Followers: 0 Kudos [?]: 15 [0], given: 1 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 16 Dec 2012, 03:01 let the two elements be 1 and 2,element 1 in alloy A =5/8 , element 1 in alloy B=1/3, element 1 in mixture=x, therefore 4/3=(1/3-x)/(5/8-x)= ½ so the answer is (A). _________________ www.mnemoniceducation.com TURN ON YOUR MINDS!!! Verbal Forum Moderator Status: Preparing for the another shot...! Joined: 03 Feb 2011 Posts: 1425 Location: India Concentration: Finance, Marketing GPA: 3.75 Followers: 129 Kudos [?]: 647 [0], given: 62 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 16 Dec 2012, 03:07 Expert's post Another approach to this problem is by weighted average. In such problems , it becomes easier if we stick to one metal only. So the compostion of first metal in A is 5/8 and and in B is 1/3. So when we combine A and B, the compostion will be between 5/8 and 1/3. Now in the diagram attached: The "distance" between the compositions of first metal in A and B is 7/24. The composition of the final mixture is given as 4:3 i.e. A's 4 parts and B's 3 parts. But when we interpret in the distance format, the sequence flips i.e. the distance between final mixture and A will be 3 units and that of between final mixture and B will be 4 units. Now to calculate the compostion of the first metal in X, add the 4 units to 1/3. i.e. 4/7 *7/24 +1/3 OR subtract 3 units from 5/8 i.e. 5/8 - 4/7* 7/24. This will come out as 50%. Therefore the other metal will also constitute 50%. Hence the ratio is 1:1. +1A Attachments solution.png [ 13.08 KiB | Viewed 4640 times ] _________________ Intern Joined: 05 Sep 2011 Posts: 7 Followers: 0 Kudos [?]: 1 [0], given: 1 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 10 Apr 2013, 20:19 VeritasPrepKarishma wrote: farukqmul wrote: Two alloys A and B are composed of two basic elements. The ratios of the compositions of the two basic elements in the two alloys are 5 : 3 and 1 : 2, respectively. A new alloy X is formed by mixing the two alloys A and B in the ratio 4 : 3. What is the ratio of the composition of the two basic elements in alloy X ? (A) 1 : 1 (B) 2 : 3 (C) 5 : 2 (D) 4 : 3 (E) 7 : 9 Responding to a pm: When you need to find the average, it is better to use the formula in its original form: Avg = (C1*w1 + C2*w2)/(w1 + w2) Avg = [(5/8)*4 + (1/3)*3]/(4+3) = 1/2 Ratio of the 2 elements in the mixture = 1:1 Obviously the formula will work in the other form too though it is best to use that when you need to find the ratio of the weights. Using the formula in the other form: w1/w2 = (A2 - Aavg)/(Aavg - A1) element 1 in A = 5/8 element 1 in B = 1/3 element 1 in mixture = x 4/3 = (1/3 - x) / (x - 5/8) 4/3(x - 5/8) = 1/3 - x (7/3)x = 7/6 x = 1/2 (You made a calculation error) Ratio of elements in the mixture = 1:1 Dear karishma thanks a lot. that's a great solution but one point is subtle to me. would you please explain which part of the question indicates that we should go with weighted average formula? thanks again in advance. Regards Posted from my mobile device Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 4877 Location: Pune, India Followers: 1156 Kudos [?]: 5378 [0], given: 165 Re: Two alloys A and B are composed of two basic elements. The [#permalink] 11 Apr 2013, 06:15 Expert's post marzan2011 wrote: Dear karishma thanks a lot. that's a great solution but one point is subtle to me. would you please explain which part of the question indicates that we should go with weighted average formula? thanks again in advance. Regards Posted from my mobile device It's a matter of practice. You will never be given 'find the weighted average'. When you have two things (classes, groups, mixtures, solutions) and they talk about the total, average or something, that should give you a hint that weighted average might work here. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Save$100 on Veritas Prep GMAT Courses And Admissions Consulting
Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.

Veritas Prep Reviews

CEO
Joined: 09 Sep 2013
Posts: 2856
Followers: 207

Kudos [?]: 43 [0], given: 0

Re: Two alloys A and B are composed of two basic elements. The [#permalink]  13 Oct 2014, 05:40
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: Two alloys A and B are composed of two basic elements. The   [#permalink] 13 Oct 2014, 05:40
Similar topics Replies Last post
Similar
Topics:
1 Two sets, A and B, have the same number of elements 3 01 May 2013, 21:55
There are two bars of gold-silver alloy; one piece has 2 5 29 May 2008, 01:15
There are two bars of gold-silver alloy; The first is 40% 1 12 Mar 2008, 10:20
There are two bars of gold-silver alloy; one piece has 2 2 11 Nov 2007, 12:05
1 A sales staff is composed of a sales manager and two sales 5 15 Jan 2006, 02:02
Display posts from previous: Sort by

# Two alloys A and B are composed of two basic elements. The

 Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO 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®.