GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 23 Jan 2020, 05:05

### 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

# A teacher administers a test to two classes. She adds 15 points to eac

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 60625
A teacher administers a test to two classes. She adds 15 points to eac  [#permalink]

### Show Tags

03 Dec 2019, 01:22
00:00

Difficulty:

55% (hard)

Question Stats:

70% (02:25) correct 30% (03:06) wrong based on 46 sessions

### HideShow timer Statistics

A teacher administers a test to two classes. She adds 15 points to each student’s score in the first class and 10 points to each student’s score in the second class, which increases the overall average of the two classes by 13.5 points. If the ratio of the number of students in the first class to the number of students in the second class is p:q where p and q are positive integers with no common factors, what is the value of p+q?

A. 8
B. 9
C. 10
D. 11
E. 13

Are You Up For the Challenge: 700 Level Questions

_________________
Manager
Joined: 10 Dec 2017
Posts: 176
Location: India
Re: A teacher administers a test to two classes. She adds 15 points to eac  [#permalink]

### Show Tags

03 Dec 2019, 02:33
Bunuel wrote:
A teacher administers a test to two classes. She adds 15 points to each student’s score in the first class and 10 points to each student’s score in the second class, which increases the overall average of the two classes by 13.5 points. If the ratio of the number of students in the first class to the number of students in the second class is p:q where p and q are positive integers with no common factors, what is the value of p+q?

A. 8
B. 9
C. 10
D. 11
E. 13

Are You Up For the Challenge: 700 Level Questions

10........13.5........15
-3.5 +1.5
Wq/Wp=Q/P=1.5/3.5
P/Q=3.5/1.5
Since P and Q are integers and have no common factors
P/Q=7/3
P+Q=10
C:)
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 5719
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: A teacher administers a test to two classes. She adds 15 points to eac  [#permalink]

### Show Tags

03 Dec 2019, 03:08
total avg ; 13.5
class A = 15 points is 1.5 away and class B = 10 points is 3.5 away
ratio ; 1.5:3.5 ; 3:7
p+q = 10
IMO C

Bunuel wrote:
A teacher administers a test to two classes. She adds 15 points to each student’s score in the first class and 10 points to each student’s score in the second class, which increases the overall average of the two classes by 13.5 points. If the ratio of the number of students in the first class to the number of students in the second class is p:q where p and q are positive integers with no common factors, what is the value of p+q?

A. 8
B. 9
C. 10
D. 11
E. 13

Are You Up For the Challenge: 700 Level Questions
Yale Moderator
Joined: 05 May 2019
Posts: 163
GPA: 3
A teacher administers a test to two classes. She adds 15 points to eac  [#permalink]

### Show Tags

06 Dec 2019, 02:19
The Answer is C
Algebraic Method

For Class 1 - Sum of Scores = S1, and P(or multiple of P) Students. Either way, P works.
For Class 2 - Sum of Scores = S2, and Q(similar to P) Students.

The average of the two classes increases by 13.5 marks.
Equate this to get $$\frac{(S1+15P)+(S2+10Q)}{P+Q} = \frac{S1+S2}{P+Q}+13.5$$

Simplify and get $$\frac{P}{Q}=\frac{3.5}{1.5}$$

convert to integer form and simplify further to get $$\frac{P}{Q}=\frac{7}{3}$$

This is the reduced form (no common factors). Add and get $$P+Q = 10$$
A teacher administers a test to two classes. She adds 15 points to eac   [#permalink] 06 Dec 2019, 02:19
Display posts from previous: Sort by

# A teacher administers a test to two classes. She adds 15 points to eac

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne