NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 21:14 It is currently 26 Apr 2024, 21:14
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

If each of the students in a certain mathematics class is

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
udaymathapati
Manager
Manager
Joined: 06 Apr 2010
Posts: 93
Own Kudos [?]: 4922 [8]
Given Kudos: 15
Send PM
Reviews Badge
If each of the students in a certain mathematics class is [#permalink] New post   23 Aug 2010, 08:54
3
Kudos
5
Bookmarks
00:00
A
B
C
D
E

Difficulty:

15% (low)

Question Stats:

78% (01:11) correct 22% (01:19) wrong based on 393 sessions
Hide Show timer Statistics
If each of the students in a certain mathematics class is either a junior or a senior, how many students are in the class?

(1) If one student is to be chosen at random from the class to attend a conference, the probability that the student chosen will be a senior is 4/7.
(2) There are 5 more seniors in the class than juniors.
ShowHide Answer
Official Answer
C
Most Helpful Reply
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92948
Own Kudos [?]: 619261 [9]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
Re: If each of the students in a certain mathematics class is [#permalink] New post   23 Aug 2010, 09:24
4
Kudos
5
Bookmarks
Expert Reply
udaymathapati wrote:
If each of the students in a certain mathematics class is either a junior or a senior, how many students are in the class?
(1) If one student is to be chosen at random from the class to attend a conference,
the probability that the student chosen will be a senior is 4/7.
(2) There are 5 more seniors in the class than juniors.


Let the # of seniors in the class be \(s\) and the # of juniors be \(j\). Question: \(s+j=?\)

(1) If one student is to be chosen at random from the class to attend a conference, the probability that the student chosen will be a senior is 4/7 --> \(\frac{s}{s+j}=\frac{4}{7}\) --> \(3s=4j\): two variables, hence not sufficient to calculate \(s+j\).

(2) There are 5 more seniors in the class than juniors --> \(s=j+5\). Clearly not sufficient to calculate \(s+j\).

(1)+(2) We have two different linear equations with 2 variables, hence we can find the values of both variables and calculate \(s+j\). Sufficient.

Answer: C.
General Discussion
User avatar
B
gota900
Intern
Intern
Joined: 15 Aug 2018
Posts: 38
Own Kudos [?]: 9 [0]
Given Kudos: 49
GMAT 1: 740 Q47 V45
GPA: 3.5
Send PM
Re: If each of the students in a certain mathematics class is [#permalink] New post   24 Dec 2018, 03:21
Bunuel wrote:
udaymathapati wrote:
If each of the students in a certain mathematics class is either a junior or a senior, how many students are in the class?
(1) If one student is to be chosen at random from the class to attend a conference,
the probability that the student chosen will be a senior is 4/7.
(2) There are 5 more seniors in the class than juniors.


Let the # of seniors in the class be \(s\) and the # of juniors be \(j\). Question: \(s+j=?\)

(1) If one student is to be chosen at random from the class to attend a conference, the probability that the student chosen will be a senior is 4/7 --> \(\frac{s}{s+j}=\frac{4}{7}\) --> \(3s=4j\): two variables, hence not sufficient to calculate \(s+j\).

(2) There are 5 more seniors in the class than juniors --> \(s=j+5\). Clearly not sufficient to calculate \(s+j\).

(1)+(2) We have two different linear equations with 2 variables, hence we can find the values of both variables and calculate \(s+j\). Sufficient.

Answer: C.


Just out of curiosity:

Is the total number 35???
User avatar
S
Jagan212
Intern
Intern
Joined: 06 Apr 2018
Posts: 36
Own Kudos [?]: 36 [0]
Given Kudos: 33
Location: India
Schools: IIMC MBAEx'23 (D) IIMA PGPX'23
GMAT 1: 620 Q43 V32
GPA: 3.2
Send PM
Re: If each of the students in a certain mathematics class is [#permalink] New post   14 Aug 2020, 09:33
gota900 wrote:
Bunuel wrote:
udaymathapati wrote:
If each of the students in a certain mathematics class is either a junior or a senior, how many students are in the class?
(1) If one student is to be chosen at random from the class to attend a conference,
the probability that the student chosen will be a senior is 4/7.
(2) There are 5 more seniors in the class than juniors.


Let the # of seniors in the class be \(s\) and the # of juniors be \(j\). Question: \(s+j=?\)

(1) If one student is to be chosen at random from the class to attend a conference, the probability that the student chosen will be a senior is 4/7 --> \(\frac{s}{s+j}=\frac{4}{7}\) --> \(3s=4j\): two variables, hence not sufficient to calculate \(s+j\).

(2) There are 5 more seniors in the class than juniors --> \(s=j+5\). Clearly not sufficient to calculate \(s+j\).

(1)+(2) We have two different linear equations with 2 variables, hence we can find the values of both variables and calculate \(s+j\). Sufficient.

Answer: C.


Just out of curiosity:

Is the total number 35???


Let the no. of seniors = \(s\) and no. of juniors = \(j\). We need to find \(s+j\)

1) \(P(s) = \frac{4}{7}\)
\(\frac{s}{s+j} = \frac{4}{7}\)
\(=> 3s = 4j\) INSUFFICIENT. Strike out A and D. Hold B, C, and E

2) There are 5 more seniors in the class than juniors
\(s = j+5\) INSUFFICIENT. Strike out B. Hold C and E

1) + 2)
\(3s = 4j\)
\(s = j+5\)
Solve the above two equations to get \(s+j = 35\). SUFFICIENT. Strike out E. Choose the correct answer C.
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32691
Own Kudos [?]: 822 [0]
Given Kudos: 0
Send PM
Re: If each of the students in a certain mathematics class is [#permalink] New post   15 Apr 2023, 21:01
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
gmatclubot
Re: If each of the students in a certain mathematics class is [#permalink]
15 Apr 2023, 21:01
Moderator:
Bunuel
Math Expert
92948 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions