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

 It is currently 22 Nov 2018, 03:34

# GMAT Club Tests are Free and Open until midnight Nov 22, Pacific Time

### 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

## Events & Promotions

###### Events & Promotions in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
• ### Key Strategies to Master GMAT SC

November 24, 2018

November 24, 2018

07:00 AM PST

09:00 AM PST

Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
• ### GMATbuster's Weekly GMAT Quant Quiz

November 24, 2018

November 24, 2018

09:00 AM PST

11:00 AM PST

We will start promptly at 09 AM Pacific Time. Quiz will last approximately 2 hours. Make sure you are on time or you will be at a disadvantage.

# If 20% of a class averages 80% on a test, 50% of the class averages 60

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50772
If 20% of a class averages 80% on a test, 50% of the class averages 60  [#permalink]

### Show Tags

24 Jan 2016, 04:48
1
00:00

Difficulty:

5% (low)

Question Stats:

94% (01:30) correct 6% (01:04) wrong based on 61 sessions

### HideShow timer Statistics

If 20% of a class averages 80% on a test, 50% of the class averages 60% on the test, and the remainder of the class averages 40% on the test, what is the overall class average?

A. 80%
B. 74%
C. 58%
D. 56%
E. 50%

_________________
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12901
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: If 20% of a class averages 80% on a test, 50% of the class averages 60  [#permalink]

### Show Tags

25 Jan 2016, 14:43
Hi All,

This question is a Weighted Average question with a series of dependent variables. It can be solved Algebraically or by TESTing VALUES.

We're told that:
1) 20% of a class averages 80% on a test
2) 50% of the class averages 60% on the test
3) the remainder of the class averages 40% on the test

We're asked for the overall class average.

Since the class can be broken down into 3 groups, and the first two groups represent 20% and 50%, the third group represents 30% of the class. While it might be tempting to use 100 students when we TEST VALUES, it will actually be easier to use 10 total students instead...

2 students scored 80%
5 students scored 60%
3 students scored 40%

(2)(80) + 5(60) + 3(40) =
160 + 300 + 120 =
580

580/10 students = 58 --> 58% average

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!*****

Math Expert
Joined: 02 Aug 2009
Posts: 7047
If 20% of a class averages 80% on a test, 50% of the class averages 60  [#permalink]

### Show Tags

25 Jan 2016, 19:11
Bunuel wrote:
If 20% of a class averages 80% on a test, 50% of the class averages 60% on the test, and the remainder of the class averages 40% on the test, what is the overall class average?

A. 80%
B. 74%
C. 58%
D. 56%
E. 50%

Apart from the calculations method we can get down to two choices by merely looking at the info..
20%-80%marks..
50%-60% marks..
30%-40%marks..

1)Here once we see the max concentration is 60% and the other two sets are at equidistant from 60% with slight bias towards 40%.
so our answer has to be slightly less than 60..
A and B are straightway out as they are >60.. E too is far off ..
finally we are left with only C and D.. now we are left with only 2 to answer..

2)Lets do it by weighted average..
first take weighted average for outer values..
20%-80%marks..
30%-40%marks..

the difference 80-40=40 is divided into five equal parts (due to ratio 20:30)..
so each part is 8.
since 40% has more weight we will add lesser of 2 parts: 3 parts to it..
40 + 2*8=56..
now we have two set of people..
50%-56%marks..
50%-60% marks..

equal numbers for 60 and 56, so ans (60+56)/2=58
C
_________________

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

Intern
Joined: 02 Feb 2016
Posts: 27
Location: United States
GMAT 1: 710 Q49 V38
GPA: 3.5
Re: If 20% of a class averages 80% on a test, 50% of the class averages 60  [#permalink]

### Show Tags

10 Oct 2017, 08:05
Total Marks = (20x80)+(50x60)+(30x40) = 5800
Total Class weight = 100

Weighted avg = 5800/100 = 58
Re: If 20% of a class averages 80% on a test, 50% of the class averages 60 &nbs [#permalink] 10 Oct 2017, 08:05
Display posts from previous: Sort by

# If 20% of a class averages 80% on a test, 50% of the class averages 60

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

 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®.