GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 22 Jul 2018, 04:03

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

Solution A is 40% chlorine by volume, and Solution B is 60% chlorine

  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: 47168
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 00:05
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

92% (00:57) correct 8% (01:27) wrong based on 78 sessions

HideShow timer Statistics

Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons

_________________

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

Expert Post
1 KUDOS received
examPAL Representative
User avatar
S
Joined: 07 Dec 2017
Posts: 507
Re: Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 00:15
1
Bunuel wrote:
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons


As mixture problems can often be solved based on properties of ratios, without explicit calculation, we'll look for such a solution.
This is a Logical approach.

We'd like the final concentration of chlorine in the tank to be 50%, exactly in the middle of the concentrations of solution A (40%) and solution B (60%).
That is, we want both of the solutions to affect the final concentration equally, meaning we want them to have equal volumes.
Since there were 40 gallons fo Solution A, we need to add 40 gallons of Solution B.

(A) is our answer.

*Note: if the conentration weren't exactly in the middle, we would have needed to adjust accordingly. Say we want the final concentration to be 45%. This is 5% away from Solution A and 15% away from solution B for a ratio of 1:3. Then we need 3 times as much solution A as solution B (this ensure is has '3 times the effect' and our answer would be 40/3 gallons.
_________________

David
Senior tutor at examPAL
Signup for a free GMAT course
Image
We won some awards:
Image
Save up to $250 on examPAL packages (special for GMAT Club members)

Expert Post
SVP
SVP
User avatar
P
Joined: 08 Jul 2010
Posts: 2120
Location: India
GMAT: INSIGHT
WE: Education (Education)
Reviews Badge
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 02:18
Bunuel wrote:
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons


Please find the solution as attached.

Two methods mentioned.

Answer: option A
Attachments

File comment: www.GMATinsight.com
GMATINSIGHT.jpg
GMATINSIGHT.jpg [ 1.15 MiB | Viewed 817 times ]


_________________

Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION

VP
VP
avatar
P
Joined: 07 Dec 2014
Posts: 1037
Re: Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 11:21
Bunuel wrote:
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons


let x=gallons of solution B to be added
.4*40+.6*x=.5(40+x)
x=40 gallons
A
SC Moderator
avatar
D
Joined: 22 May 2016
Posts: 1835
Premium Member CAT Tests
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 12:06
Bunuel wrote:
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons

10-second method:
The final solution's concentration (50%) is the average of A's (40%) and B's (60%) concentrations.

That can happen only if A and B have identical volumes. B's volume = A's = 40 gallons

Answer A

Weighted average:

One version of weighted average formula:
(% A)(Vol A) + (% B)(Vol B) = (% of A+B)(Vol A+B)

A = 40% chlorine = .40
B = .60 chlorine
A's volume = 40
B's volume = x

\(.40(40) +.60(x) = .50(40+x)\)
\(16 + .60x = 20 + .50x\)
\(.10x = 4\)
\(x=\frac{4}{.1}=\frac{40}{1}=40\)
gallons

Answer A
_________________

In the depths of winter, I finally learned
that within me there lay an invincible summer.

-- Albert Camus, "Return to Tipasa"

Manager
Manager
avatar
B
Joined: 08 Sep 2016
Posts: 116
Re: Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 10 Apr 2018, 14:31
40A + 60B = 50A + 50B

10B = 10A

A/B = 1/1

For 1A added, there's 1B added since the ratio is 1 to 1. So if 40 gallons of A is in the tank, 40 gallons of B will need to be added to maintain the ratio.
Answer A
Expert Post
Target Test Prep Representative
User avatar
G
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 2973
Location: United States (CA)
Re: Solution A is 40% chlorine by volume, and Solution B is 60% chlorine  [#permalink]

Show Tags

New post 11 Apr 2018, 16:19
Bunuel wrote:
Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine?

A. 40 gallons
B. 50 gallons
C. 60 gallons
D. 80 gallons
E. 100 gallons



Current there are 40 x 0.4 = 16 gallons of chlorine from solution A. We can let the amount of solution B = n and create the equation:

(16 + 0.6n)/(40 + n) = 1/2

2(16 + 0.6n) = 40 + n

32 + 1.2n = 40 + n

0.2n = 8

n = 40

Answer: A
_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: Solution A is 40% chlorine by volume, and Solution B is 60% chlorine &nbs [#permalink] 11 Apr 2018, 16:19
Display posts from previous: Sort by

Solution A is 40% chlorine by volume, and Solution B is 60% chlorine

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

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.