Find all School-related info fast with the new School-Specific MBA Forum

It is currently 28 Jul 2016, 06:25
GMAT Club Tests

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A student's average (arithmetic mean) test score on 4 tests

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

Hide Tags

Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 34105
Followers: 6098

Kudos [?]: 76725 [1] , given: 9981

A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 26 Aug 2012, 03:07
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

91% (01:45) correct 9% (00:49) wrong based on 735 sessions

HideShow timer Statistics

Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 34105
Followers: 6098

Kudos [?]: 76725 [1] , given: 9981

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 26 Aug 2012, 03:08
1
This post received
KUDOS
Expert's post
SOLUTION:

A student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80
(B) 82
(C) 84
(D) 86
(E) 88

Since the student's average test score on 4 tests is 78, then the sum of the first 4 test scores is 4*78=312. We need the sum of ALL 5 scores to be 5*80=400, so if \(x\) is the 5th test score, then \(312+x=400\) --> \(x=88\).

Answer: E.
_________________

New to the Math Forum?
Please read this: 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

Senior Manager
Senior Manager
User avatar
Status: Prevent and prepare. Not repent and repair!!
Joined: 13 Feb 2010
Posts: 275
Location: India
Concentration: Technology, General Management
GPA: 3.75
WE: Sales (Telecommunications)
Followers: 9

Kudos [?]: 68 [0], given: 282

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 26 Aug 2012, 08:13
Let the score in the 5th test be x.
The sum of the first 4 tests = 78*4=312
Now it implies 312+x/5=80
Therefore x=88
_________________

I've failed over and over and over again in my life and that is why I succeed--Michael Jordan
Kudos drives a person to better himself every single time. So Pls give it generously
Wont give up till i hit a 700+

Intern
Intern
avatar
Joined: 21 Apr 2010
Posts: 12
Followers: 1

Kudos [?]: 0 [0], given: 2

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 27 Aug 2012, 11:15
(sum of x)/4 = 78
So (sum of x) = 312.
Now (sum of x + x5)/5=80
So (312+x5)=400 i.e. x5=88.
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 34105
Followers: 6098

Kudos [?]: 76725 [0], given: 9981

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 31 Aug 2012, 02:11
Expert's post
SOLUTION:

A student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80
(B) 82
(C) 84
(D) 86
(E) 88

Since the student's average test score on 4 tests is 78, then the sum of the first 4 test scores is 4*78=312. We need the sum of ALL 5 scores to be 5*80=400, so if \(x\) is the 5th test score, then \(312+x=400\) --> \(x=88\).

Answer: E.
_________________

New to the Math Forum?
Please read this: 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

1 KUDOS received
Manager
Manager
User avatar
Joined: 13 Feb 2012
Posts: 147
Location: Italy
Concentration: General Management, Entrepreneurship
GMAT 1: 560 Q36 V34
GPA: 3.1
WE: Sales (Transportation)
Followers: 4

Kudos [?]: 6 [1] , given: 85

A students average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 15 Dec 2012, 08:28
1
This post received
KUDOS
I follow Manhattan advice on this one and write the average formula as a first thing:

in order to reach an average of 80 over 5 test the students has to reach 400 points; he now has 78*4= 312.

400-312= 88.

Answer E
_________________

"The Burnout" - My Debrief

Kudos if I helped you ;)


Andy

Intern
Intern
User avatar
Joined: 24 Apr 2012
Posts: 48
Followers: 0

Kudos [?]: 21 [0], given: 1

Re: A students average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 16 Dec 2012, 04:17
Ans:
total score after 4 tests=312 and score needed after 5 tests= 5x80=400 the student scores the difference in the 5th test which is 88 , (E).
_________________

www.mnemoniceducation.com

TURN ON YOUR MINDS!!!

1 KUDOS received
Intern
Intern
avatar
Joined: 04 Apr 2013
Posts: 31
Followers: 0

Kudos [?]: 13 [1] , given: 4

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 12 Apr 2013, 10:42
1
This post received
KUDOS
Examining the known average can simply things. We need to reach 80. We currently have 78, four times. 78 is -2 away from 80. Having this four times weights our average -8 off what is desires. To 'catch up' to the average in one test, we must make up the full 8 point deficit in one test. We need an 88. 88 - 8 = 80.
Current Student
User avatar
Joined: 23 Oct 2010
Posts: 386
Location: Azerbaijan
Concentration: Finance
Schools: HEC '15 (A)
GMAT 1: 690 Q47 V38
Followers: 21

Kudos [?]: 275 [0], given: 73

GMAT ToolKit User
Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 19 Jun 2013, 00:56
(80-78)=2
2*5tests=10

78+10=88
_________________

Happy are those who dream dreams and are ready to pay the price to make them come true

I am still on all gmat forums. msg me if you want to ask me smth

1 KUDOS received
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 37

Kudos [?]: 1607 [1] , given: 193

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 06 Jun 2014, 02:56
1
This post received
KUDOS
Let students score be

78..... 78..... 78....... 78

Average after 5th test should be 80

So score in 5th exam should at least be 80 & also it should "cover up the loses" in the earlier tests

Loses earlier = 2 per test = 2 * 4 = 8

80 + 8 = 88

Answer = E
_________________

Kindly press "+1 Kudos" to appreciate :)

1 KUDOS received
Manager
Manager
avatar
Joined: 15 Aug 2013
Posts: 58
Followers: 0

Kudos [?]: 17 [1] , given: 5

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 06 Jun 2014, 06:08
1
This post received
KUDOS
I will suggest a little different solution (not a very great trick) but very useful for finding averages since it can save your "TIME" at the tests...
Average of 5 tests to be 80 suggests - in each test the student scored 80 (and this can make average 80). SO -
In 5th test the student has to score 80 for sure, plus any deficit to make up for the average. We know in 4 tests his averge was 78, which means he is 2 markes short of average(80 in this case) in previous 4 tests and he has to make up for this deficit in the 5th test. Hence he has to score 2 * 4 (deficit * no of tests) = 8. Remember, he has to score 80 also in the 5th test.
Hence in total - 80 + 8 = 88. Choice E



Here is how I would approach - 80 in the 5th test, and 2 *4 = 8 totl 88 n the 5th tests. SO it took few seconds to do the ques... Practise this kind of technique while solving questions n averages has been very handy for m... All the best!!
Intern
Intern
avatar
Joined: 05 Jul 2014
Posts: 1
Followers: 0

Kudos [?]: 0 [0], given: 8

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 05 Jul 2014, 08:04
zerosleep wrote:
I will suggest a little different solution (not a very great trick) but very useful for finding averages since it can save your "TIME" at the tests...
Average of 5 tests to be 80 suggests - in each test the student scored 80 (and this can make average 80). SO -
In 5th test the student has to score 80 for sure, plus any deficit to make up for the average. We know in 4 tests his averge was 78, which means he is 2 markes short of average(80 in this case) in previous 4 tests and he has to make up for this deficit in the 5th test. Hence he has to score 2 * 4 (deficit * no of tests) = 8. Remember, he has to score 80 also in the 5th test.
Hence in total - 80 + 8 = 88. Choice E



Here is how I would approach - 80 in the 5th test, and 2 *4 = 8 totl 88 n the 5th tests. SO it took few seconds to do the ques... Practise this kind of technique while solving questions n averages has been very handy for m... All the best!!



Thanks zerosleep.. I always followed traditional approach.. now i would try your way when encountered with question on averages
Manager
Manager
avatar
Joined: 07 Apr 2014
Posts: 147
Followers: 1

Kudos [?]: 19 [0], given: 81

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 10 Sep 2014, 03:39
Bunuel wrote:
A student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80
(B) 82
(C) 84
(D) 86
(E) 88

Practice Questions
Question: 30
Page: 156
Difficulty: 600


total of 4 test = 4*78 = 312
if the mean of 5 test has to be 80 then total has to be 400.

400-312=88.

so in the fifth test the score should be 88 for the mean to become 80
Intern
Intern
avatar
Joined: 06 Nov 2014
Posts: 13
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 16 Nov 2014, 08:40
(4*78+x)/5=80
x=(5*80)-(4*78) ok so 5*78-4*78= 78,
x= 5*(80-78) + 78 --> 5*2+78
total score required 78+10=88
Manager
Manager
avatar
Joined: 23 Sep 2015
Posts: 170
Schools: Insead Sept '17
GMAT 1: 690 Q47 V38
GMAT 2: 700 Q48 V38
Followers: 0

Kudos [?]: 27 [0], given: 46

Premium Member
Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 23 Nov 2015, 11:51
Alternative approach : (New data - Old avg)/New number of items in the set = change in average
(New - 78) /5 = 2
New = 88
Manager
Manager
User avatar
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 152
Followers: 7

Kudos [?]: 29 [0], given: 2

Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 25 May 2016, 07:18
Bunuel wrote:
A student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80
(B) 82
(C) 84
(D) 86
(E) 88


To solve, we use the average equation:

average = sum/quantity

We don't know the individual scores for each of the first 4 tests, but because their average is 78, we can think of the first 4 scores as 4 scores of 78 each. We then multiply 78 by 4 to get the sum of those four tests:

78 x 4 = 312

Let's let n = the score on the 5th test. Thus, the sum of the 5 tests is 312 + 5th test score, or 312 + n. Also, because the new average will be 80, we substitute 80 for the new average. We can now solve for n.

Average = sum/quantity

80 = (312 + n)/5

400 = 312 + n

88 = n

The answer is E.
_________________

Image
Jeffrey Miller
Jeffrey Miller
Head of GMAT Instruction

Director
Director
User avatar
Joined: 18 Oct 2014
Posts: 856
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
Followers: 57

Kudos [?]: 123 [0], given: 58

GMAT ToolKit User CAT Tests
Re: A student's average (arithmetic mean) test score on 4 tests [#permalink]

Show Tags

New post 25 May 2016, 08:46
Bunuel wrote:
A student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80
(B) 82
(C) 84
(D) 86
(E) 88

Practice Questions
Question: 30
Page: 156
Difficulty: 600


To have avg score of 80 implies that student needs 80 marks in all 5 tests.

That means 2 marks increase in all 4 tests= 4*2= 8 total marks increase in 4 tests + 80 marks in 5th tests= 88 marks

E is the answer
_________________

I welcome critical analysis of my post!! That will help me reach 700+

Re: A student's average (arithmetic mean) test score on 4 tests   [#permalink] 25 May 2016, 08:46
    Similar topics Author Replies Last post
Similar
Topics:
The average (arithmetic mean) score on a test taken by 10 students was AbdurRakib 1 15 Jun 2016, 01:18
1 Experts publish their posts in the topic Joe’s average (arithmetic mean) test score across 4 equally weighted Bunuel 3 07 Feb 2016, 10:56
1 Experts publish their posts in the topic Jerry’s average (arithmetic mean) score on the first 3 of 4 tests is 8 Bunuel 5 27 Dec 2015, 09:12
13 Experts publish their posts in the topic 20 students took the test. The arithmetic mean of the scores guerrero25 5 04 Aug 2013, 04:00
5 Experts publish their posts in the topic A students average (arithmetic mean) test score on 4 tests petercao 5 11 Nov 2008, 13:33
Display posts from previous: Sort by

A student's average (arithmetic mean) test score on 4 tests

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

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®.