Last visit was: 13 Jun 2024, 23:55 It is currently 13 Jun 2024, 23:55
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.
Close
Request Expert Reply
Confirm Cancel
SORT BY:
Date
Tags:
Difficulty: Sub 505 Level,    Probability,                
Show Tags
Hide Tags
Math Expert
Joined: 02 Sep 2009
Posts: 93696
Own Kudos [?]: 631600 [18]
Given Kudos: 82280
Send PM
Math Expert
Joined: 02 Sep 2009
Posts: 93696
Own Kudos [?]: 631600 [3]
Given Kudos: 82280
Send PM
Senior Manager
Senior Manager
Joined: 02 Dec 2014
Posts: 304
Own Kudos [?]: 300 [3]
Given Kudos: 353
Location: Russian Federation
Concentration: General Management, Economics
GMAT 1: 640 Q44 V33
WE:Sales (Telecommunications)
Send PM
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10147
Own Kudos [?]: 16829 [2]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
2
Kudos
Expert Reply
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

In a certain class, one student is to be selected at random to read. What is the probability that a boy will read?

(1) Two-thirds of the students in the class are boys.
(2) Ten of the students in the class are girls.


In general, when one con is number and the other con is ratio, it is most likely that ratio is an answer. Also, since fraction=proability, que:probability and in 1) 2/3:fraction. Therefore, the answer is A.


-> from con 1) and con 2), if one of the conditions is given by numbers and the other is given by ratio (percent,fraction), then the condition with ratio (percent,fraction) value has higher chance of being the answer.
Target Test Prep Representative
Joined: 04 Mar 2011
Status:Head GMAT Instructor
Affiliations: Target Test Prep
Posts: 3042
Own Kudos [?]: 6449 [1]
Given Kudos: 1646
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
1
Kudos
Expert Reply
Bunuel wrote:
In a certain class, one student is to be selected at random to read. What is the probability that a boy will read?

(1) Two-thirds of the students in the class are boys.
(2) Ten of the students in the class are girls.


We need to determine the probability that a boy will be selected to read, in a class of boys and girls.

Statement One Alone:

Two-thirds of the students in the class are boys.

Since we know that 2/3 of the class are boys, we know that the probability of randomly selecting a boy to read is 2/3. Statement one alone is sufficient to answer the question. We can eliminate answer choices B, C, and E.

Statement Two Alone:

Ten of the students in the class are girls.

Without knowing the number of boys in the class, we cannot determine the probability that a boy will be selected to read. Statement two alone is not sufficient to answer the question.

Answer: A
Manager
Manager
Joined: 12 Jun 2016
Posts: 145
Own Kudos [?]: 232 [0]
Given Kudos: 151
Location: India
Concentration: Technology, Leadership
WE:Sales (Telecommunications)
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
Hi!

This may sound stupid to ask, but are we not assuming that the student we pick can read? I mean, I could not see anywhere in the stem that says the student we pick is capable of reading.

Originally posted by susheelh on 02 Sep 2017, 07:19.
Last edited by susheelh on 02 Sep 2017, 08:19, edited 1 time in total.
Math Expert
Joined: 02 Sep 2009
Posts: 93696
Own Kudos [?]: 631600 [1]
Given Kudos: 82280
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
1
Kudos
Expert Reply
susheelh wrote:
Hi!

This may sound stupid to ask, but are we not assuming that the student we pick can read? I mean, I could not see anywhere in the stem that every student we pick is capable of reading.


It's safe to assume that a student can read...
Manager
Manager
Joined: 12 Jun 2016
Posts: 145
Own Kudos [?]: 232 [0]
Given Kudos: 151
Location: India
Concentration: Technology, Leadership
WE:Sales (Telecommunications)
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
Thanks Bunuel for the answer!

Its just that this is a DS question. I marked it as E since I thought some of the students can't read. Maybe this happened since I have a young son whom I am still not able to teach how to read :-D

I get it now. Its safe to assume everyone can read.

Bunuel wrote:
susheelh wrote:
Hi!

This may sound stupid to ask, but are we not assuming that the student we pick can read? I mean, I could not see anywhere in the stem that every student we pick is capable of reading.


It's safe to assume that a student can read...
Senior Manager
Senior Manager
Joined: 29 Jun 2017
Posts: 312
Own Kudos [?]: 806 [0]
Given Kudos: 76
GPA: 4
WE:Engineering (Transportation)
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
Ans is A

1)Let 6x students , then 4x boys
selecting 1 boy out of 4x = 4x and out of 6x is 6x
so P = 4x/6x = 2/3 , Sufficient


2)total number of girls = 10 , insufficient as number of boys are unknown. D eliminated
Manager
Manager
Joined: 19 Jul 2017
Posts: 71
Own Kudos [?]: 25 [0]
Given Kudos: 85
Location: India
Concentration: General Management, Strategy
GPA: 3.5
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
Bunuel wrote:
In a certain class, one student is to be selected at random to read. What is the probability that a boy will read?

(1) Two-thirds of the students in the class are boys.
(2) Ten of the students in the class are girls.

Practice Questions
Question: 3
Page: 275
Difficulty: 550



Two-thirds of the students in the class are boys. S1 gives the desired outcome/total possibilities as 2/3. So clearly sufficient.

Statement 2 gives no clue abt the total students or the number of boys. Insufficient.

Ans:A
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 33551
Own Kudos [?]: 837 [0]
Given Kudos: 0
Send PM
Re: In a certain class, one student is to be selected at random to read. [#permalink]
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
Re: In a certain class, one student is to be selected at random to read. [#permalink]
Moderator:
Math Expert
93696 posts