Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 29 May 2017, 03:05

### 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 June
Open Detailed Calendar

# A professor gave the same exam to two classes. The 200

Author Message
Senior Manager
Joined: 07 Jan 2008
Posts: 400
Followers: 3

Kudos [?]: 243 [0], given: 0

A professor gave the same exam to two classes. The 200 [#permalink]

### Show Tags

19 Jun 2008, 05:03
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (02:49) wrong based on 4 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A professor gave the same exam to two classes. The 200 students in the first class scored an average (arithmetic mean) of a 75 on the exam. The students in the second class scored an average (arithmetic mean) of an 85 on the exam. If the average (arithmetic mean) score of students in both classes was a 77, how many students are in the second class?

A. 50
B. 75
C. 150
D. 64
E. 80
Director
Joined: 14 Aug 2007
Posts: 729
Followers: 10

Kudos [?]: 197 [0], given: 0

### Show Tags

19 Jun 2008, 05:44
lexis wrote:
A professor gave the same exam to two classes. The 200 students in the first class scored an average (arithmetic mean) of a 75 on the exam. The students in the second class scored an average (arithmetic mean) of an 85 on the exam. If the average (arithmetic mean) score of students in both classes was a 77, how many students are in the second class?

A. 50
B. 75
C. 150
D. 64
E. 80

A.50

200*75 + x*85 = 77(x+200); x = 50
CEO
Joined: 29 Mar 2007
Posts: 2562
Followers: 21

Kudos [?]: 453 [0], given: 0

### Show Tags

19 Jun 2008, 05:57
lexis wrote:
A professor gave the same exam to two classes. The 200 students in the first class scored an average (arithmetic mean) of a 75 on the exam. The students in the second class scored an average (arithmetic mean) of an 85 on the exam. If the average (arithmetic mean) score of students in both classes was a 77, how many students are in the second class?

A. 50
B. 75
C. 150
D. 64
E. 80

(200*75+85x)/(200+x)=77 ---> 200*75+85x=200*77+77x --> 8x=200*77-200*75 --> 8x=200(77-75)

8x=400 --> x=50
Senior Manager
Joined: 07 Feb 2008
Posts: 313
Followers: 2

Kudos [?]: 146 [0], given: 1

### Show Tags

19 Jun 2008, 06:40
lexis wrote:
A professor gave the same exam to two classes. The 200 students in the first class scored an average (arithmetic mean) of a 75 on the exam. The students in the second class scored an average (arithmetic mean) of an 85 on the exam. If the average (arithmetic mean) score of students in both classes was a 77, how many students are in the second class?

A. 50
B. 75
C. 150
D. 64
E. 80

A = 50

200(75) + x(85) = 77(200 + x)

= 50
CEO
Joined: 17 Nov 2007
Posts: 3585
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 576

Kudos [?]: 3986 [0], given: 360

### Show Tags

21 Jun 2008, 11:11
another approach for fast calculation:

$$\frac{77-75}{85-77}=\frac14=\frac{x}{200}$$ --> $$x=\frac{200}{4}=50$$
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

Re: PS: Average   [#permalink] 21 Jun 2008, 11:11
Display posts from previous: Sort by

# A professor gave the same exam to two classes. The 200

 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®.