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

It is currently 23 Jul 2014, 02:38

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

There are 17 students in a certain class. On the day the te

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
avatar
Joined: 10 Apr 2012
Posts: 265
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE: Project Management (Telecommunications)
Followers: 2

Kudos [?]: 78 [0], given: 318

GMAT ToolKit User Premium Member CAT Tests
There are 17 students in a certain class. On the day the te [#permalink] New post 17 Mar 2013, 06:00
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

94% (02:08) correct 6% (00:54) wrong based on 67 sessions
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?

A. 78
B. 80
C. 87
D. 91
E. 94


I took this question from Magoosh . I saw somebody coming up with a very quick solution -

"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94."

approach is unclear :(

I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .


As always , thank you !
[Reveal] Spoiler: OA
Kaplan Promo CodeKnewton GMAT Discount CodesVeritas Prep GMAT Discount Codes
Expert Post
2 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18693
Followers: 3233

Kudos [?]: 22239 [2] , given: 2602

Re: There are 17 students in a certain class. On the day the te [#permalink] New post 17 Mar 2013, 06:08
2
This post received
KUDOS
Expert's post
guerrero25 wrote:
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?

A. 78
B. 80
C. 87
D. 91
E. 94


I took this question from Magoosh . I saw somebody coming up with a very quick solution -

"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94."

approach is unclear :(

I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .


As always , thank you !


Say all 16 students got 77 (so the average is naturally 77).

Now, what should be the 17th student score in order the average to be 78? If all 17 had 78 then the average would be 78, but 16 have 77, so Taqeesha should get 78+16*1=94.

Hope it's clear.

_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18693
Followers: 3233

Kudos [?]: 22239 [1] , given: 2602

Re: There are 17 students in a certain class. On the day the te [#permalink] New post 17 Mar 2013, 06:11
1
This post received
KUDOS
Expert's post
Bunuel wrote:
guerrero25 wrote:
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?

A. 78
B. 80
C. 87
D. 91
E. 94


I took this question from Magoosh . I saw somebody coming up with a very quick solution -

"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94."

approach is unclear :(

I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .


As always , thank you !


Say all 16 students got 77 (so the average is naturally 77).

Now, what should be the 17th student score in order the average to be 78? If all 17 had 78 then the average would be 78, but 16 have 77, so Taqeesha should get 78+16*1=94.

Hope it's clear.


Another example: two students got 5 points each, how much should the third student get in order the average to be 10?

10+2*5=20.

Hope it helps.

_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
avatar
Joined: 10 Apr 2012
Posts: 265
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE: Project Management (Telecommunications)
Followers: 2

Kudos [?]: 78 [0], given: 318

GMAT ToolKit User Premium Member CAT Tests
Re: There are 17 students in a certain class. On the day the te [#permalink] New post 17 Mar 2013, 07:01
Makes sense . Thanks Bunuel !


I found this thread that has more example . Posting it here just to help somebody like me in search of Average tricks .

average-accelerated-guide-to-solve-averages-quickly-77148.html


Regards
Intern
Intern
avatar
Joined: 10 Jan 2013
Posts: 17
GMAT 1: 640 Q41 V38
WE: Marketing (Transportation)
Followers: 2

Kudos [?]: 11 [0], given: 8

Re: There are 17 students in a certain class. On the day the te [#permalink] New post 18 Apr 2013, 13:42
I went with the following

77*16=1232

78*17=1326

1326-1232=94

94 was the score.

Hope it makes sense
Manager
Manager
avatar
Joined: 26 Feb 2013
Posts: 184
Followers: 0

Kudos [?]: 17 [0], given: 25

Re: There are 17 students in a certain class. On the day the te [#permalink] New post 16 Oct 2013, 02:56
Bunuel wrote:
guerrero25 wrote:
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?

A. 78
B. 80
C. 87
D. 91
E. 94


I took this question from Magoosh . I saw somebody coming up with a very quick solution -

"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94."

approach is unclear :(

I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .


As always , thank you !


Say all 16 students got 77 (so the average is naturally 77).

Now, what should be the 17th student score in order the average to be 78? If all 17 had 78 then the average would be 78, but 16 have 77, so Taqeesha should get 78+16*1=94.

Hope it's clear.


Bunuel,
What are we adding here? It seems to me that we are adding score+number of students = score? Can you please explain?
Btw I did it the long way as described above.
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18693
Followers: 3233

Kudos [?]: 22239 [0], given: 2602

Re: There are 17 students in a certain class. On the day the te [#permalink] New post 16 Oct 2013, 03:19
Expert's post
Skag55 wrote:
Bunuel wrote:
guerrero25 wrote:
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?

A. 78
B. 80
C. 87
D. 91
E. 94


I took this question from Magoosh . I saw somebody coming up with a very quick solution -

"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94."

approach is unclear :(

I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .


As always , thank you !


Say all 16 students got 77 (so the average is naturally 77).

Now, what should be the 17th student score in order the average to be 78? If all 17 had 78 then the average would be 78, but 16 have 77, so Taqeesha should get 78+16*1=94.

Hope it's clear.


Bunuel,
What are we adding here? It seems to me that we are adding score+number of students = score? Can you please explain?
Btw I did it the long way as described above.


We are adding average score (78) and surplus score (16*1), so that the average to be 78.

_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: There are 17 students in a certain class. On the day the te   [#permalink] 16 Oct 2013, 03:19
    Similar topics Author Replies Last post
Similar
Topics:
In a class of 30 students, there are 17 girls and 13 boys. axl_oz 8 24 Oct 2008, 13:16
On a given day, 50 students in a certain class took a math arjtryarjtry 3 22 Jul 2008, 18:17
In a class of 30 students, there are 17 girls and 13 boys. prasannar 2 28 Jun 2008, 00:06
In a class of 30 students, 17 students study Chinese, and r appuvar 3 28 Oct 2007, 13:39
In a class of 30 students, 17 students study Chinese, and r maaverick 5 19 Mar 2005, 12:54
Display posts from previous: Sort by

There are 17 students in a certain class. On the day the te

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| 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®.