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

It is currently 19 May 2019, 13:56

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

Of the test animals in a laboratory, 60% are brown rats and 40% are

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

Hide Tags

 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 55150
Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 29 Aug 2017, 23:52
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

91% (01:37) correct 9% (00:42) wrong based on 72 sessions

HideShow timer Statistics

Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces

_________________
SVP
SVP
User avatar
V
Joined: 26 Mar 2013
Posts: 2174
Reviews Badge CAT Tests
Re: Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 31 Aug 2017, 11:03
1
Bunuel wrote:
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces


No need to calculate.

If we have equal number of rates, it means average wight will be in the middle = 8.45. However, there is greater number of brown rats, So the average will tend be slightly higher than 8.45. So it will be 8.6

Answer: D
Current Student
User avatar
P
Joined: 18 Aug 2016
Posts: 618
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
GMAT ToolKit User Reviews Badge
Re: Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 30 Aug 2017, 00:09
Bunuel wrote:
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces


Suppose their are 10 rats
(9.2*6 + 7.7*4)/10 = (55.2+30.8 = 86)/10 = 8.6
D
9.2-7.7 = 1.5 divided in 6:4 ratio would be 0.9 and 0.6
9.2-0.6 = 8.6
D
_________________
We must try to achieve the best within us


Thanks
Luckisnoexcuse
Intern
Intern
avatar
Joined: 15 Jul 2017
Posts: 7
Re: Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 30 Aug 2017, 00:12
0.6*9.2+0.4*7.7=5.52+3.08=8.6 so D is correct

Goal+Plan=Success (GPS)
Manager
Manager
User avatar
G
Joined: 27 Dec 2016
Posts: 232
Concentration: Marketing, Social Entrepreneurship
GPA: 3.65
WE: Marketing (Education)
Reviews Badge
Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 30 Aug 2017, 00:30
Bunuel wrote:
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces


- Let the number of total animal : 100, so brown rats (BR) = 60 and black rats (BL) = 40.
- \(Average weight = \frac{{number of BR}*{BR's average weight}+{number of BL}*{BL's average weight}}{Total Animal} = \frac{(60*9.2)+(40*7.7)}{100} =\) 8.6 ounces.

D.
_________________
There's an app for that - Steve Jobs.
Senior PS Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3386
Location: India
GPA: 3.12
Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 31 Aug 2017, 11:21
Let the number of rats be x

It has been given the brown rats are 60%(average weight - 9.2)
Also, the black rats are 40%(weight weight - 7.7)

From the questions stem, \(\frac{.6x * 9.2 + .4x * 7.7}{x} =\frac{5.52x + 3.08x}{x} = 8.6\)(Option D)
_________________
You've got what it takes, but it will take everything you've got
Target Test Prep Representative
User avatar
D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 6133
Location: United States (CA)
Re: Of the test animals in a laboratory, 60% are brown rats and 40% are  [#permalink]

Show Tags

New post 02 Sep 2017, 07:29
Bunuel wrote:
Of the test animals in a laboratory, 60% are brown rats and 40% are black rats. If the average brown rat weighs 9.2 ounces and the average black rat weighs 7.7 ounces, what is the average weight of a rat in the laboratory?

A. 7.7 ounces
B. 8.1 ounces
C. 8.45 ounces
D. 8.6 ounces
E. 9.2 ounces


We create the following equation for a weighted mean:

0.6(9.2) + 0.4(7.7) = 5.52 + 3.08 = 8.6

Do we have to write questions about test animals in laboratories? Isn’t there a better theme that we can come up with?

Answer: D
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

GMAT Club Bot
Re: Of the test animals in a laboratory, 60% are brown rats and 40% are   [#permalink] 02 Sep 2017, 07:29
Display posts from previous: Sort by

Of the test animals in a laboratory, 60% are brown rats and 40% are

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


Copyright

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®.