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

It is currently 20 Aug 2019, 19:55

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

Jim needs to mix a solution in the following ratio: 1 part bleach for

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

Hide Tags

Find Similar Topics 
Manager
Manager
User avatar
Joined: 28 May 2009
Posts: 144
Location: United States
Concentration: Strategy, General Management
GMAT Date: 03-22-2013
GPA: 3.57
WE: Information Technology (Consulting)
GMAT ToolKit User
Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post Updated on: 16 May 2019, 21:00
1
1
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

65% (01:34) correct 35% (01:49) wrong based on 50 sessions

HideShow timer Statistics

Jim needs to mix a solution in the following ratio: 1 part bleach for every 4 parts water. When mixing the solution, Jim makes a mistake and mixes in half as much bleach as he ought to have. The total solution consists of 18 mL. How much did Jim put into the solution?

A. 1mL
B. 2mL
C. 3mL
D. 4mL
E. 5mL

To solve this problem:
The ratio is 1:4, meaning there should be x parts bleach and 4x parts water. However, Jim put in half as much bleach as he should have, so he put in \(\frac{x}{2}\) parts bleach. So the equation would be:
\(\frac{x}{2} + 4x = 18\) \(=> x=4\)
This part is clear, however, according to the MGMAT Guide the correct answer is not \(4\), but it's \(\frac{4}{2}\), but we already used \(\frac{x}{2}\) in the equation.

Now, \(4(2) + 2 = 18\) which makes sense. However, my main concern is with the reasoning, that to solve the equation, we have already halved Jim's amount, and then we are halving it again. Please explain.

_________________

Originally posted by megafan on 06 Nov 2012, 13:46.
Last edited by Bunuel on 16 May 2019, 21:00, edited 2 times in total.
Renamed the topic.
Director
Director
User avatar
Status: Done with formalities.. and back..
Joined: 15 Sep 2012
Posts: 580
Location: India
Concentration: Strategy, General Management
Schools: Olin - Wash U - Class of 2015
WE: Information Technology (Computer Software)
GMAT ToolKit User Reviews Badge
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post 06 Nov 2012, 20:29
megafan wrote:
I can not seem grasp the reasoning behind the Answer to the below question:

Jim needs to mix a solution in the following ratio: 1 part bleach for every 4 parts water. When mixing the solution, Jim makes a mistake and mixes in half as much bleach as he ought to have. The total solution consists of 18 mL. How much did Jim put into the solution?

To solve this problem:
The ratio is 1:4, meaning there should be x parts bleach and 4x parts water. However, Jim put in half as much bleach as he should have, so he put in \(\frac{x}{2}\) parts bleach. So the equation would be:
\(\frac{x}{2} + 4x = 18\) \(=> x=4\)
This part is clear, however, according to the MGMAT Guide the correct answer is not \(4\), but it's \(\frac{4}{2}\), but we already used \(\frac{x}{2}\) in the equation.

Now, \(4(2) + 2 = 18\) which makes sense. However, my main concern is with the reasoning, that to solve the equation, we have already halved Jim's amount, and then we are halving it again. Please explain.


if you look at the equation that you've set up. you would notice that you actually added x/2 part of bleach in 4x water not x part. Thus if x=4, the amount of bleach is x/2=4/2.
It is not x that you are looking for, but the value that you used in mixture ie x/2
_________________
Lets Kudos!!! ;-)
Black Friday Debrief
Intern
Intern
avatar
Joined: 28 Feb 2013
Posts: 8
Location: India
Concentration: Strategy, Social Entrepreneurship
GMAT 1: 740 Q48 V42
GPA: 3.45
WE: General Management (Non-Profit and Government)
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post 24 May 2013, 20:46
megafan wrote:
I can not seem grasp the reasoning behind the Answer to the below question:

Jim needs to mix a solution in the following ratio: 1 part bleach for every 4 parts water. When mixing the solution, Jim makes a mistake and mixes in half as much bleach as he ought to have. The total solution consists of 18 mL. How much did Jim put into the solution?

To solve this problem:
The ratio is 1:4, meaning there should be x parts bleach and 4x parts water. However, Jim put in half as much bleach as he should have, so he put in \(\frac{x}{2}\) parts bleach. So the equation would be:
\(\frac{x}{2} + 4x = 18\) \(=> x=4\)
This part is clear, however, according to the MGMAT Guide the correct answer is not \(4\), but it's \(\frac{4}{2}\), but we already used \(\frac{x}{2}\) in the equation.

Now, \(4(2) + 2 = 18\) which makes sense. However, my main concern is with the reasoning, that to solve the equation, we have already halved Jim's amount, and then we are halving it again. Please explain.


1 part bleach for every 4 parts water = 1:4
1/2 part bleach for every 4 parts water = 1/2 : 4 = 1:8

9x = 18
x = 2 <-- Answer
Intern
Intern
avatar
Joined: 30 May 2013
Posts: 12
GMAT 1: 680 Q48 V35
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post 06 Jun 2013, 15:30
as vy3rgc mentioned, 1/2:4 ratio is a 1:8 ratio.

I figured it out this way.
in a 10 part solution, there is 2 bleach and 8 water.
Jim only added 1/2 the amount of bleach needed so instead of 2 bleach he added 1 bleach and 8 water.
This also changes it from a 10 part mixed solution to a 9 part mixed solution.

In a 18 part solution with this mistake, he'll have 2 parts bleach and 16 parts water.
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 14824
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post 08 Apr 2015, 23:29
Hi All,

While this is an old series of posts, there is a rather straight-forward way to approach this question that is more about real-world math than anything else.

The original prompt tells us that Jim needs to mix a solution in the following ratio: 1 part bleach for every 4 parts water.

So, if we have 1 part bleach + 4 parts water we get 5 parts total mixture....

Next, we're told that when mixing the solution, Jim makes a mistake and mixes in half as much bleach as he ought to have.

So, he ACTUALLY mixed 1/2 part bleach + 4 parts water and gets 4.5 parts total mixture....

The total solution consists of 18 mL. How much did Jim put into the solution?

18 = (4.5)(4) so the 18mL is made up of 4 "sets" of the 4.5 parts mixture. This means there are 4(4) = 16 mL of water and 4(1/2) = 2mL of bleach.

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

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

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/
Director
Director
User avatar
P
Joined: 14 Feb 2017
Posts: 933
Location: Australia
Concentration: Technology, Strategy
Schools: LBS '22
GMAT 1: 560 Q41 V26
GMAT 2: 550 Q43 V23
GMAT 3: 650 Q47 V33
GMAT 4: 650 Q44 V36
WE: Management Consulting (Consulting)
Reviews Badge CAT Tests
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for  [#permalink]

Show Tags

New post 04 Aug 2019, 16:53
Think about this logically.
The intended ratio is 1 part bleach per 4 parts water
Bleach:water: total
1:4: 5

He mixes in 1/2 as much bleach or, in other words, twice as much water, so the ratio is actually
Bleach:water: total
1:8:9

Thus the amount of bleach present
= 1/9 * 18
= 2 units
_________________
Goal: Q49, V41

+1 Kudos if you like my post pls!
GMAT Club Bot
Re: Jim needs to mix a solution in the following ratio: 1 part bleach for   [#permalink] 04 Aug 2019, 16:53
Display posts from previous: Sort by

Jim needs to mix a solution in the following ratio: 1 part bleach for

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





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne