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

It is currently 26 Jun 2016, 04:59
GMAT Club Tests

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A mixture of sand and cement contains, 3 parts of sand and 5

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

Hide Tags

2 KUDOS received
Current Student
User avatar
Joined: 28 Apr 2012
Posts: 311
Location: India
Concentration: Finance, Technology
GMAT 1: 650 Q48 V31
GMAT 2: 770 Q50 V47
WE: Information Technology (Computer Software)
Followers: 20

Kudos [?]: 329 [2] , given: 142

A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 01 Jun 2014, 12:14
2
This post received
KUDOS
10
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

39% (02:53) correct 61% (01:27) wrong based on 185 sessions

HideShow timer Statistics

A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT
[Reveal] Spoiler: OA

_________________

"Appreciation is a wonderful thing. It makes what is excellent in others belong to us as well."
― Voltaire


Press Kudos, if I have helped.
Thanks!

Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 33504
Followers: 5931

Kudos [?]: 73486 [1] , given: 9902

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 01 Jun 2014, 15:05
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT


We have total of 8 parts: 3 parts of sand and 5 parts of cement.

In order there to be half sand and half cement (4 parts of sand and 4 parts of cement), we should remove 1 part of cement. With 1 part of cement comes 3/5 parts of sand, so we should remove 1 + 3/5 = 8/5 part of the mixture, which is (8/5)/8 = 1/5 of the mixture.

Answer: C.
_________________

New to the Math Forum?
Please read this: 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

1 KUDOS received
Intern
Intern
avatar
Joined: 08 Aug 2011
Posts: 17
Followers: 1

Kudos [?]: 67 [1] , given: 17

GMAT ToolKit User
Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 02 Jun 2014, 13:32
1
This post received
KUDOS
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8


This is just a weighted average question, so we can apply the formula for that: with \(C\) as the concentrations and \(V\) as the volumes...


\(C_1*\frac{V_1}{V_1 + V_2} + C_2*\frac{V_2}{V_1 + V_2} = C_{final}\)

If sand:cement=3:5, then the concentration of sand in the initial mixture is \(\frac{3}{8}\). Since we are asked for the proportion of the mixture that should be replaced, we can assume a total volume of \(1\) and let \(x\) be the "amount" of the mixture to be replaced by pure sand (i.e., concentration of 1). We can then write the following equation:

\((\frac{3}{8})*(1-x) + (1)*(x)=\frac{1}{2}\)

Thus, \(x=\frac{1}{5}\)
Expert Post
2 KUDOS received
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 6666
Location: Pune, India
Followers: 1828

Kudos [?]: 11105 [2] , given: 218

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 02 Jun 2014, 21:15
2
This post received
KUDOS
Expert's post
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT


You can use the scale method here too.

A mix has 3/8 of sand. Another is all sand so fraction of sand is 1. You have to mix them to get 1/2 sand.

w1/w2 = (1 - 1/2)/(1/2 - 3/8) = 4/1

So the mix should be 4 parts and only sand should be 1 part. Hence 1/5 of the mix must have been replaced by sand.

Answer (C)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 36

Kudos [?]: 1564 [0], given: 193

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 04 Jun 2014, 02:08
Initial

Sand ............... Cement ............... Total

\(\frac{3}{8}\) ..................... \(\frac{5}{8}\) ...................... 1

Requirement

\(\frac{4}{8} ..................... \frac{4}{8} ..................... 1\)

Just focus on cement:

To have \(\frac{4}{8}\) cement, we require to remove

\(\frac{5}{8} - \frac{4}{8} = \frac{1}{8}\)cement

In Mixture, the portion of cement is \(\frac{5}{8};\)so to remove \(\frac{1}{8}\) cement, mixture required to be removed

\(= \frac{\frac{1}{8} * 1}{\frac{5}{8}}\)

\(= \frac{1}{5}\)

Answer = C
_________________

Kindly press "+1 Kudos" to appreciate :)

Manager
Manager
User avatar
Joined: 11 Feb 2014
Posts: 61
Followers: 0

Kudos [?]: 31 [0], given: 25

GMAT ToolKit User
Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 25 Jun 2014, 16:42
Bunuel wrote:
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT


We have total of 8 parts: 3 parts of sand and 5 parts of cement.

In order there to be half sand and half cement (4 parts of sand and 4 parts of cement), we should remove 1 part of cement. With 1 part of cement comes 3/5 parts of sand, so we should remove 1 + 3/5 = 8/5 part of the mixture, which is (8/5)/8 = 1/5 of the mixture.

Answer: C.


Bunuel: I do not quite understand the highlighted section above. 1 part of the mixture will contain 3/8 sand and 5/8 cement. How did you come up with "1 part of cement contains 3/5 parts of sand"?
2 KUDOS received
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 36

Kudos [?]: 1564 [2] , given: 193

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 25 Jun 2014, 21:01
2
This post received
KUDOS
One more method:

Sand ............. Cement .............. Total

\(\frac{3}{8}\) .................. \(\frac{5}{8}\) ........................ 1

Let "x" quantity of mixture be removed;

\(\frac{3}{8} - \frac{3x}{8}\) ........... \(\frac{5}{8} - \frac{5x}{8}\) ............... 1 - x

Adding "x" quantity of sand

\(\frac{3}{8} - \frac{3x}{8} + x\) .......... \(\frac{5}{8} - \frac{5x}{8}\) .............. 1-x+x

Resultant should be half sand & half cement

Two options to set up the equation

Option I

\(\frac{3}{8} - \frac{3x}{8} + x = \frac{1}{2}\)

\(x = \frac{1}{5}\)

Option II

\(\frac{5}{8} - \frac{5x}{8} = \frac{1}{2}\)

\(x = \frac{1}{5}\)

Answer = C
_________________

Kindly press "+1 Kudos" to appreciate :)

1 KUDOS received
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 36

Kudos [?]: 1564 [1] , given: 193

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 25 Jun 2014, 21:09
1
This post received
KUDOS
Game wrote:
Bunuel wrote:
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT


We have total of 8 parts: 3 parts of sand and 5 parts of cement.

In order there to be half sand and half cement (4 parts of sand and 4 parts of cement), we should remove 1 part of cement. With 1 part of cement comes 3/5 parts of sand, so we should remove 1 + 3/5 = 8/5 part of the mixture, which is (8/5)/8 = 1/5 of the mixture.

Answer: C.


Bunuel: I do not quite understand the highlighted section above. 1 part of the mixture will contain 3/8 sand and 5/8 cement. How did you come up with "1 part of cement contains 3/5 parts of sand"?



Not Bunuel, but seems I can explain it

Mixture .................. Sand ............... Cement

1 ............................ \(\frac{3}{8}\) ................... \(\frac{5}{8}\)

Multiply by \(\frac{8}{5}\) to all above

\(\frac{8}{5}\) ........................ \(\frac{3}{8} * \frac{8}{5}\) ............. \(\frac{5}{8} * \frac{8}{5}\)


\(\frac{8}{5}\) ........................ \(\frac{3}{5}\) ....................... 1

From the above, we can say that 1 part of cement comes with \(\frac{3}{5}\) parts of sand in \(\frac{8}{5}\) quantity of mixture.
_________________

Kindly press "+1 Kudos" to appreciate :)

Senior Manager
Senior Manager
User avatar
Joined: 17 Dec 2012
Posts: 433
Location: India
Followers: 22

Kudos [?]: 352 [0], given: 14

A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 25 Jun 2014, 21:19
S1 - 3 parts element 1 , 5 parts element 2
S2 - x parts of mixture removed i.e, -(3/8 * x) parts element 1, -(5/8 * x) parts element 2
S3 - x parts of element 1 added

We thus have 3 - (3*x)/8 +x / 5 - (5*x)/8 = 1/1
x=1.6 . i.e, 1.6/8 = 1/5 of the mixture removed.
_________________

Srinivasan Vaidyaraman
Sravna
http://www.sravnatestprep.com

Classroom Courses in Chennai

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 10190
Followers: 481

Kudos [?]: 124 [0], given: 0

Premium Member
Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 18 Aug 2015, 23:18
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.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Manager
Manager
User avatar
Joined: 10 Jun 2015
Posts: 128
Followers: 1

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

A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 18 Aug 2015, 23:53
ConnectTheDots wrote:
A mixture of sand and cement contains, 3 parts of sand and 5 parts of cement. How much of the mixture must be substituted with sand to make the mixture half sand and half cement?

A. 1/3
B. 1/4
C. 1/5
D. 1/7
E. 1/8

Source: Indian CAT

It is easier to answer this type of question using allegation rule.
3/8 parts are sand in the original mixture.
we are adding with only sand to make the new mixture 1:1
therefore, 1/1 part is sand that we add.
3/8 1/1

1/2

1/2 : 1/8
so, the ratio is 1/2 : 1/8 or 4:1
That is, if you remove 4 parts from the original mixture and add 1 part sand, the resultant mixture is 1:1
To elaborate further, if the original mixture is 8 kg (3 kg sand and 5 kg cement), you remove 4 kg of the mixture which contains 1.5 kg sand and 2.5 kg of cement.
Now, add 1 kg of sand. The new mixture becomes 2.5 kg of sand and 2.5 kg of cement.
Senior Manager
Senior Manager
avatar
Joined: 07 Dec 2014
Posts: 277
Followers: 1

Kudos [?]: 30 [0], given: 0

A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 06 Sep 2015, 15:53
let x=fraction of mixture to be substituted
3/8-3x/8+x=1/2
x=1/5

Last edited by gracie on 11 Nov 2015, 20:39, edited 1 time in total.
Intern
Intern
avatar
Joined: 06 Jun 2014
Posts: 1
Concentration: Finance, Operations
GPA: 3.64
Followers: 0

Kudos [?]: 0 [0], given: 7

Re: A mixture of sand and cement contains, 3 parts of sand and 5 [#permalink]

Show Tags

New post 07 Sep 2015, 13:36
How can we use the alligation method/shortcut to solve this?

My attempt:

Sand...................Cement
3/8......................5/8
.......\.................../
.........\............../
..............4/8
Re: A mixture of sand and cement contains, 3 parts of sand and 5   [#permalink] 07 Sep 2015, 13:36
    Similar topics Author Replies Last post
Similar
Topics:
5 Experts publish their posts in the topic A certain type of concrete mixture is to be made of cement, sand and g RSOHAL 3 22 Dec 2015, 15:56
3 Experts publish their posts in the topic In 1 kg mixture of sand and iron, 20% is iron. How much sand qlx 3 17 Mar 2014, 06:40
Experts publish their posts in the topic If cement, gravel and sand are to be mixed in 7:10:13 antoxavier 1 21 Feb 2013, 08:10
81 Experts publish their posts in the topic 10kg of a mixture contains 30% sand and 70% clay. In order t tejal777 37 14 Aug 2009, 17:56
11 If 200 lb of a mixture contain 80% husk and 20% sand. Then tejal777 20 13 Aug 2009, 03:27
Display posts from previous: Sort by

A mixture of sand and cement contains, 3 parts of sand and 5

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


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

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®.