probability DS...

Expert replies

singhpreet1: Senior | Next Rank: 100 Posts; Posts: 95; Joined: Tue Jun 08, 2010 11:27 am; Thanked: 7 times

by singhpreet1 » Sat Jun 12, 2010 12:30 am

In a group of 30 students, 8 are enrolled in an English class and 16 are enrolled in an Algebra class. How many students are enrolled in both an English and an Algebra class?

(1) 20 are enrolled in exactly one of these two classes.

(2) 3 are not enrolled in either of these classes.

i can result to B. only St. 2 is sufficient, 30-3=27,8+16+24; 27-24, therefore 3 must be studying both..your take guyz...

Preet

Like this post

Source: Beat The GMAT — Data Sufficiency | Sat Jun 12, 2010 12:30 am

ankurmit: Legendary Member; Posts: 516; Joined: Mon Nov 02, 2009 6:42 amFollowed by: 1 member; Location: Mumbai; Thanked: 14 times; GMAT Score:710

by ankurmit » Sat Jun 12, 2010 1:13 am

ans must be B

Like this post

singhpreet1: Senior | Next Rank: 100 Posts; Posts: 95; Joined: Tue Jun 08, 2010 11:27 am; Thanked: 7 times

by singhpreet1 » Sat Jun 12, 2010 4:44 am

ankurmit wrote:ans must be B

Ankur: request you to show your working to establish B, though i do agree with your answer!

Thanks.

Like this post

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

by Stuart@KaplanGMAT » Sat Jun 12, 2010 7:46 pm

singhpreet1 wrote:In a group of 30 students, 8 are enrolled in an English class and 16 are enrolled in an Algebra class. How many students are enrolled in both an English and an Algebra class?

(1) 20 are enrolled in exactly one of these two classes.

(2) 3 are not enrolled in either of these classes.

i can result to B. only St. 2 is sufficient, 30-3=27,8+16+24; 27-24, therefore 3 must be studying both..your take guyz...

Preet

The question is flawed. What's the source?

On the GMAT, language is very specific. When we see the phrase "8 are enrolled in an English class", we know nothing else about those people. For example, some of them could also be enrolled in the Algebra class.

Accordingly, statement (2) is impossible. If there are 30 students total, and 8 are in English and 16 in Algebra, then there must be at least 6 people (30 - 24) who aren't enrolled in either class.

If the question stem read "8 are enrolled only in an English class and 16 are enrolled only in an Algebra class", then (2) would make sense (and be sufficient).

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course

Like this post

mj78ind: Master | Next Rank: 500 Posts; Posts: 265; Joined: Mon Dec 28, 2009 9:45 pmFollowed by: 2 members; Thanked: 26 times; GMAT Score:760

by mj78ind » Fri Jun 18, 2010 6:32 pm

Stuart Kovinsky wrote:
singhpreet1 wrote:In a group of 30 students, 8 are enrolled in an English class and 16 are enrolled in an Algebra class. How many students are enrolled in both an English and an Algebra class?

(1) 20 are enrolled in exactly one of these two classes.

(2) 3 are not enrolled in either of these classes.

i can result to B. only St. 2 is sufficient, 30-3=27,8+16+24; 27-24, therefore 3 must be studying both..your take guyz...

Preet
The question is flawed. What's the source?

On the GMAT, language is very specific. When we see the phrase "8 are enrolled in an English class", we know nothing else about those people. For example, some of them could also be enrolled in the Algebra class.

Accordingly, statement (2) is impossible. If there are 30 students total, and 8 are in English and 16 in Algebra, then there must be at least 6 people (30 - 24) who aren't enrolled in either class.

If the question stem read "8 are enrolled only in an English class and 16 are enrolled only in an Algebra class", then (2) would make sense (and be sufficient).

Interesting, I had a side question Stuart. Please refer attached file what I did per the stem of the questions is make the following 3 equations:
X + Z = 8
Y +Z = 16
X + Y +Z + N = 30

And then went with the stmts, 1 gives me the 4th eqtn and so does stmt 2. Hence, I chose the answer D without solving fully (where I would have found the error in the question) to save time.

On the GMAT - is the above strategy correct or should I solve the question fully just to be sure?

Attachments

Sets.doc: Sets file; (20.5 KiB) Downloaded 89 times

Like this post

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

by Stuart@KaplanGMAT » Fri Jun 18, 2010 8:20 pm

mj78ind wrote:Interesting, I had a side question Stuart. Please refer attached file what I did per the stem of the questions is make the following 3 equations:
X + Z = 8
Y +Z = 16
X + Y +Z + N = 30

And then went with the stmts, 1 gives me the 4th eqtn and so does stmt 2. Hence, I chose the answer D without solving fully (where I would have found the error in the question) to save time.

On the GMAT - is the above strategy correct or should I solve the question fully just to be sure?

On the GMAT, you don't have to worry about flawed questions - so your methodology would be just fine.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review