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

 It is currently 26 May 2017, 19:45

### 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

# If a child is randomly selected from Columbus elementary sch

Author Message
TAGS:

### Hide Tags

Intern
Joined: 06 Feb 2013
Posts: 23
Followers: 0

Kudos [?]: 4 [2] , given: 3

If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

12 Oct 2013, 12:30
2
KUDOS
1
This post was
BOOKMARKED
00:00

Difficulty:

55% (hard)

Question Stats:

60% (02:17) correct 40% (01:27) wrong based on 153 sessions

### HideShow timer Statistics

If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75

(2) There are 35 more boys than there are girls
[Reveal] Spoiler: OA
Math Expert
Joined: 02 Sep 2009
Posts: 38908
Followers: 7739

Kudos [?]: 106254 [2] , given: 11618

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

12 Oct 2013, 12:41
2
KUDOS
Expert's post
If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

$$P(b)=\frac{b}{b+g}=?$$

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75 --> $$\frac{b-25}{(b-25)+g}=\frac{3}{4}$$ --> $$b-3g=25$$. Not sufficient.

(2) There are 35 more boys than there are girls --> $$g=b-35$$. Not sufficient.

(1)+(2) We have two linear equation with two unknowns ($$b-3g=25$$ and $$g=b-35$$), thus we can solve for both and get the value of $$\frac{b}{b+g}$$. Sufficient.

_________________
Intern
Joined: 06 Feb 2013
Posts: 23
Followers: 0

Kudos [?]: 4 [0], given: 3

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

12 Oct 2013, 12:49
Bunuel wrote:

$$P(b)=\frac{b}{b+g}=?$$

Thanks, Bunuel.
Could you please clarify how the statement 1 "...the probability of selecting a boy will be 0.75" is different from the question itself "what is the probability that the child will be a boy". I'm stuck here because to me it looks like they provide the same information.
Math Expert
Joined: 02 Sep 2009
Posts: 38908
Followers: 7739

Kudos [?]: 106254 [1] , given: 11618

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

12 Oct 2013, 12:51
1
KUDOS
Expert's post
LinaNY wrote:
Bunuel wrote:

$$P(b)=\frac{b}{b+g}=?$$

Thanks, Bunuel.
Could you please clarify how the statement 1 "...the probability of selecting a boy will be 0.75" is different from the question itself "what is the probability that the child will be a boy". I'm stuck here because to me it looks like they provide the same information.

(1) says that "IF 25 boys are removed from the school, the probability of selecting a boy will be 0.75"
_________________
Intern
Joined: 06 Feb 2013
Posts: 23
Followers: 0

Kudos [?]: 4 [0], given: 3

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

12 Oct 2013, 12:56
Bunuel wrote:

(1) says that "IF 25 boys are removed from the school, the probability of selecting a boy will be 0.75"

Thanks Bunuel! I totally overlooked it.
Intern
Joined: 23 Jan 2013
Posts: 7
Followers: 0

Kudos [?]: 37 [0], given: 4

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

08 Nov 2013, 05:33
Bunuel wrote:
If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

$$P(b)=\frac{b}{b+g}=?$$

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75 --> $$\frac{b-25}{(b-25)+g}=\frac{3}{4}$$ --> $$b-3g=25$$. Not sufficient.

(2) There are 35 more boys than there are girls --> $$g=b-35$$. Not sufficient.

(1)+(2) We have two linear equation with two unknowns ($$b-3g=25$$ and $$g=b-35$$), thus we can solve for both and get the value of $$\frac{b}{b+g}$$. Sufficient.

Hi Bunuel,

Can you please shed some light on why it would not be correct to state the following:

For the statement 1, p(girl)=(g/(b-25+g))=0.25.

Assuming this inference is correct, we can find the number of boys using a two equation,two unknowns approach.

Thank you!
Math Expert
Joined: 02 Sep 2009
Posts: 38908
Followers: 7739

Kudos [?]: 106254 [2] , given: 11618

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

08 Nov 2013, 05:48
2
KUDOS
Expert's post
Pmar2012 wrote:
Bunuel wrote:
If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

$$P(b)=\frac{b}{b+g}=?$$

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75 --> $$\frac{b-25}{(b-25)+g}=\frac{3}{4}$$ --> $$b-3g=25$$. Not sufficient.

(2) There are 35 more boys than there are girls --> $$g=b-35$$. Not sufficient.

(1)+(2) We have two linear equation with two unknowns ($$b-3g=25$$ and $$g=b-35$$), thus we can solve for both and get the value of $$\frac{b}{b+g}$$. Sufficient.

Hi Bunuel,

Can you please shed some light on why it would not be correct to state the following:

For the statement 1, p(girl)=(g/(b-25+g))=0.25.

Assuming this inference is correct, we can find the number of boys using a two equation,two unknowns approach.

Thank you!

Yes, it's correct but if you simplify it you'd still get the same equation: $$b-3g=25$$. Thus you'd still have only one equation with two unknowns.

Hope it's clear.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15472
Followers: 649

Kudos [?]: 209 [0], given: 0

Re: If a child is randomly selected from Columbus elementary sch [#permalink]

### Show Tags

30 Mar 2015, 05:43
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.
_________________
Re: If a child is randomly selected from Columbus elementary sch   [#permalink] 30 Mar 2015, 05:43
Similar topics Replies Last post
Similar
Topics:
1 A child selected a three-digit number, XYZ, where X, Y, and Z denote t 2 20 May 2017, 04:32
13 A ball is randomly selected from a box containing white balls and 8 08 Apr 2017, 09:45
9 Every night, Jon and his brothers randomly determine the sch 3 19 May 2017, 23:14
4 Six numbers are randomly selected and placed within a set. 4 06 Aug 2015, 13:47
12 For a trade show, two different cars are selected randomly 8 14 Jun 2016, 00:20
Display posts from previous: Sort by