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

 It is currently 18 Aug 2018, 02:05

### 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

# Solution X is 15% salt and solution Y is 50% salt.

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 02 Jan 2017
Posts: 313
Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

14 Mar 2017, 04:43
2
4
00:00

Difficulty:

15% (low)

Question Stats:

75% (00:58) correct 25% (01:20) wrong based on 150 sessions

### HideShow timer Statistics

Solution X is 15% salt and solution Y is 50% salt. If the two solutions are combined to form 7 gallons of a 30% solution, how many gallons of solution X must be used?

(A) 2

(B) 2.5

(C) 3

(D) 4

(E) 4.2
Math Expert
Joined: 02 Aug 2009
Posts: 6548
Re: Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

14 Mar 2017, 05:03
vikasp99 wrote:
Solution X is 15% salt and solution Y is 50% salt. If the two solutions are combined to form 7 gallons of a 30% solution, how many gallons of solution X must be used?

(A) 2

(B) 2.5

(C) 3

(D) 4

(E) 4.2

By Weighted Average method, we can find the ratio of X and Y..
$$\frac{X}{Y}=\frac{50-30}{30-15}=4/3$$..
So in 7 litres x is 4 and y is 3..

D
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

VP
Joined: 07 Dec 2014
Posts: 1067
Re: Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

14 Mar 2017, 17:00
vikasp99 wrote:
Solution X is 15% salt and solution Y is 50% salt. If the two solutions are combined to form 7 gallons of a 30% solution, how many gallons of solution X must be used?

(A) 2

(B) 2.5

(C) 3

(D) 4

(E) 4.2

let x=gallons of solution X to be used
.15x+.5(7-x)=.3*7
x=4
E
Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2727
Re: Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

16 Mar 2017, 13:28
1
1
vikasp99 wrote:
Solution X is 15% salt and solution Y is 50% salt. If the two solutions are combined to form 7 gallons of a 30% solution, how many gallons of solution X must be used?

(A) 2

(B) 2.5

(C) 3

(D) 4

(E) 4.2

We can let the number of gallons of solution in solution X = x and the number of gallons of solution in solution Y = y. Thus:

0.15x + 0.5y = 0.3(x + y)

15x + 50y = 30x + 30y

20y = 15x

4y = 3x

We also know that x + y = 7, or y = 7 - x, and thus:

4(7 - x) = 3x

28 - 4x = 3x

28 = 7x

x = 4

_________________

Jeffery Miller

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

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8188
Location: Pune, India
Re: Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

16 Mar 2017, 22:55
1
Here are two posts. The first one discusses the weighted average formula
w1/w2 = (A2 - Aavg)/(Aavg - A1)
and the second one discusses its application in mixtures.

https://www.veritasprep.com/blog/2011/0 ... -averages/
https://www.veritasprep.com/blog/2011/0 ... -mixtures/
_________________

Karishma
Veritas Prep GMAT Instructor

Save up to $1,000 on GMAT prep through 8/20! Learn more here > GMAT self-study has never been more personalized or more fun. Try ORION Free! Senior Manager Status: Come! Fall in Love with Learning! Joined: 05 Jan 2017 Posts: 433 Location: India Re: Solution X is 15% salt and solution Y is 50% salt. [#permalink] ### Show Tags 17 Mar 2017, 01:16 [quote="vikasp99"]Solution X is 15% salt and solution Y is 50% salt. If the two solutions are combined to form 7 gallons of a 30% solution, how many gallons of solution X must be used? (A) 2 (B) 2.5 (C) 3 (D) 4 let x amount be from soln X and y amount be from soln Y x +y = 7 0.15x + 0.5y = 0.3(x+y) solving 2 equation x = 4, y = 3 Option D _________________ GMAT Mentors EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 12189 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: Solution X is 15% salt and solution Y is 50% salt. [#permalink] ### Show Tags 18 Mar 2017, 12:39 2 Hi vikasp99, This question can be solved rather easily by TESTing THE ANSWERS. We're told to mix a certain amount of 15% salt solution with a certain amount of 50% salt solution to get a total solution that is 7 GALLONS and 30% salt. We're asked for the number of gallons of the 15% solution in that mixture. To start, if we had the SAME amount of each solution, then the mixture would be (15 + 50)/2 = 65/2 = 32.5% salt. This is clearly TOO MUCH salt, so we need MORE of the 15% solution - meaning more than 3.5 of the 7 total gallons. Thus, the correct answer must be either D or E. Let's TEST Answer D: 4 gallons IF we have.... 4 gallons of 15% 3 gallons of 50% then the average would be.... [4(.15) + 3(.5)]/7 = (.6 + 1.5)/7 = 2.1/7 = 21/70 = 3/10 = 30% This is an exact MATCH for what we were told, so this MUST be the answer. Final Answer: GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Non-Human User
Joined: 09 Sep 2013
Posts: 7751
Re: Solution X is 15% salt and solution Y is 50% salt.  [#permalink]

### Show Tags

12 May 2018, 04:54
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: Solution X is 15% salt and solution Y is 50% salt. &nbs [#permalink] 12 May 2018, 04:54
Display posts from previous: Sort by

# Events & Promotions

 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®.