GMAT Changed on April 16th - Read about the latest changes here

It is currently 22 Apr 2018, 13:01

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Ana is a girl and has the same number of brothers as sisters. Andrew

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

Hide Tags

1 KUDOS received
Manager
Manager
User avatar
Status: 2 months to go
Joined: 11 Oct 2015
Posts: 133
GMAT 1: 730 Q49 V40
GPA: 3.8
Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 06 Jul 2016, 07:02
1
This post received
KUDOS
7
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

60% (01:43) correct 40% (01:37) wrong based on 231 sessions

HideShow timer Statistics

Ana is a girl and has the same number of brothers as sisters. Andrew is a boy and has twice as many sisters as brothers. Ana and Andrew are the children of Emma. How many children does Emma have?

(A) 2
(B) 3
(C) 5
(D) 7
(E) 8

Source: Nova's Math Prep Course Book
[Reveal] Spoiler: OA
Manager
Manager
avatar
S
Joined: 29 May 2016
Posts: 124
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 06 Jul 2016, 08:18
1
This post was
BOOKMARKED
no of girls X
no of boys Y
x-1 = y
y-1 = 2x

multiple first with 2
2x-2= 2y
y-1 -2 = 2y => y=3 ignore sign
put in 1 x= 4
total 7
Intern
Intern
avatar
Joined: 08 Mar 2016
Posts: 13
GMAT ToolKit User
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 28 Jul 2016, 06:35
mbaprep2016 wrote:
no of girls X
no of boys Y
x-1 = y
y-1 = 2x

multiple first with 2
2x-2= 2y
y-1 -2 = 2y => y=3 ignore sign
put in 1 x= 4
total 7


I got the reasoning but is there a way to equate the system without having to "ignore" the sign ?
1 KUDOS received
BSchool Forum Moderator
User avatar
D
Joined: 12 Aug 2015
Posts: 2582
GRE 1: 323 Q169 V154
GMAT ToolKit User Premium Member
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 21 Apr 2017, 02:02
1
This post received
KUDOS
1
This post was
BOOKMARKED
Excellent Question.
Here is what i did in this one =>


Number of children =>

X + X + Ana=> 2X+1



Brothers in the family => X
Sisters in the family => X+1


After removing andrew =>
Brothers => X-1
Sisters => X+1

As per the question =>2(X-1)=X+1
2X-2=X+1
X=3

Hence number of children for Emma => 2X+1 => 7


SMASH THAT D.


_________________


Getting into HOLLYWOOD with an MBA

The MOST AFFORDABLE MBA programs!

STONECOLD's BRUTAL Mock Tests for GMAT-Quant(700+)

Average GRE Scores At The Top Business Schools!

Intern
Intern
avatar
B
Joined: 28 Jan 2015
Posts: 4
Location: Brazil
GMAT ToolKit User
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 14 May 2017, 07:30
mbaprep2016 wrote:
no of girls X
no of boys Y
x-1 = y
y-1 = 2x

multiple first with 2
2x-2= 2y
y-1 -2 = 2y => y=3 ignore sign
put in 1 x= 4
total 7


Actually, your second stated equation "y-1 = 2x" has a little typo.

It should be: y-1 = x/2.

Thus, you don't need to ignore the sign to achieve the solution.

(I) x-1 = y
(II) y-1 = x/2

Replacing (I) in (II):

(x-1)-1 = x/2

2(x-2) = x

2x-4 = x

x = 4

So, y = 3 and total = 7.
1 KUDOS received
Manager
Manager
User avatar
S
Joined: 01 Dec 2016
Posts: 121
Concentration: Finance, Entrepreneurship
GMAT 1: 650 Q47 V34
WE: Investment Banking (Investment Banking)
GMAT ToolKit User
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 02 Jun 2017, 04:38
1
This post received
KUDOS
Another way of solving this. Perhaps the faster way.

Actually, working with the information on ANDREW only tells you that the total number of children is a in the from (3k+1). This comes from (andrew + k brothers + 2k sisters) = Total number of children.
Total number of Children can be 1 , 4 , 7 , 10 , 13 , .....
Only Option D is matches.


By The Way: Information on ANA is useless given the answer choices.
With different answer choices, we could use this info as follows:
Because ANA has n brothers and n sisters, the total number of children is in the from (2n+1), ie ODD. This eliminates option A and E
_________________

What was previously considered impossible is now obvious reality.
In the past, people used to open doors with their hands. Today, doors open "by magic" when people approach them

Expert Post
1 KUDOS received
Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8028
Location: Pune, India
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 02 Jun 2017, 09:00
1
This post received
KUDOS
Expert's post
DensetsuNo wrote:
Ana is a girl and has the same number of brothers as sisters. Andrew is a boy and has twice as many sisters as brothers. Ana and Andrew are the children of Emma. How many children does Emma have?

(A) 2
(B) 3
(C) 5
(D) 7
(E) 8

Source: Nova's Math Prep Course Book


Just use logic:

Ana is a girl and has the same number of brothers as sisters. - this means that number of girls is 1 more than the number of boys (to imagine it, Ana is the extra girl).

Andrew is a boy and has twice as many sisters as brothers. - if that 1 extra sister and 1 fewer brother gave Andrew twice the number of sisters, we are talking about small numbers here such as 3 girls, 2 boys or 4 girls, 3 boys.
4 is twice of 2 so we must have 4 girls and 3 boys.

Answer (D)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Senior Manager
Senior Manager
avatar
S
Joined: 15 Jan 2017
Posts: 361
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 29 Aug 2017, 03:40
Thought of more as a situation than an equation --> basically it tells us:
1) Ana, apart from herself has equal no of brothers and sisters --> this rules out 2 and 3 as it clearly says brother(s) and sister(s) ('the same number of brothers as sisters') --> she is counting at least 2 of each --> buy beyond this we don't know --> she can have 3 brothers = 3 sisters; 4 brothers = 4 sister
2) Her brother Andrew, has 2x sisters than brothers --> if he had 1 bro, he'd have 2 sisters; but then that way Ana's equality rule doesn't play. So the next number: 2 brothers and 4 sisters: total 4 sisters and 3 brothers; this fits both Ana's and Andrew's rule.
5 and 8 are automatically out; leaving us with 7
Expert Post
Top Contributor
SVP
SVP
User avatar
P
Joined: 12 Sep 2015
Posts: 2298
Location: Canada
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 14 Sep 2017, 16:23
Expert's post
Top Contributor
DensetsuNo wrote:
Ana is a girl and has the same number of brothers as sisters. Andrew is a boy and has twice as many sisters as brothers. Ana and Andrew are the children of Emma. How many children does Emma have?

(A) 2
(B) 3
(C) 5
(D) 7
(E) 8


Let B = number of boys that Emma has
Let G = number of girls that Emma has

Ana is a girl and has the same number of brothers as sisters.
B = the number of brothers Ana has
Since Ana is one of Emma's girls, we know that G-1 = the number of sisters Ana has (we cannot include Ana in this count, since Ana is not her own sister)
We can write: B = G-1

Andrew is a boy and has twice as many sisters as brothers.
G = the number of sisters Andrew has
Since Andrew is one of Emma's boys, we know that B-1 = the number of brothers Andrew has
We can write: 2(B-1) = G

We now have the following system:
B = G-1
2(B-1) = G

Simplify the bottom equation to get:
B = G - 1
2B - 2 = G

Take the blue equation and replace B with G-1 to get: 2(G-1) - 2 = G
Expand: 2G - 2 - 2 = G
Solve: G = 4

When we plug G = 4 into either equation and solve for B, we get B = 3
So, B+G = 3+4 = 7
So, Emma has 7 children (3 boys and 4 girls)

Answer:
[Reveal] Spoiler:
D


Cheers,
Brent
_________________

Brent Hanneson – Founder of gmatprepnow.com

Image

MBA Blogger
User avatar
B
Joined: 19 Apr 2014
Posts: 100
Location: India
Concentration: Strategy, Technology
Schools: NTU '19
WE: Analyst (Computer Software)
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 15 Sep 2017, 00:49
7
Ana -3 brothers (boys)
-3 sisters (girls)
total 3 boys 4 girls.
Andrew: 2 brothers (boys), 4 sisters. Ana and other 3
Total 3 boys 4 girls.
Total=7


Sent from my iPhone using GMAT Club Forum
_________________

KUDOS please!! If it helped. :)
Warm Regards.
Visit My Blog

Intern
Intern
avatar
B
Joined: 24 Oct 2016
Posts: 25
GMAT ToolKit User
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 27 Sep 2017, 02:11
=> Equal number of girls and boys + Ana so 2B + Ana OR 2G + Ana
=> Girls twice the boys + Andrew so 3G + Andrew

The correct answer would be a multiple of both 2 and 3 after subtracting 1.

Option D: 7 - 1 = 6 and 6 is a multiple of both 2 and 3. So D is the right answer.
Expert Post
EMPOWERgmat Instructor
User avatar
D
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 11496
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: Ana is a girl and has the same number of brothers as sisters. Andrew [#permalink]

Show Tags

New post 06 Dec 2017, 14:50
Hi All,

This question can also be solved by 'brute force.'

We're told that:
1) Ana is female; Andrew is male
2) Ana has the SAME number of sisters as brothers
3) Andrew has TWICE as many sisters as brothers

We're asked for the total number of children in the family.

Let's start with the 3rd fact first:
Andrew COULD have
2 sisters and 1 brother
4 sisters and 2 brothers
6 sisters and 3 brothers
etc.

IF... it's 2 sisters and 1 brother, then we have
Ana and 1 other female
Andrew and 1 other male
But we're told that Ana has the SAME number of sisters as brothers (here though, she has 1 sister and 2 brothers), so this is NOT the correct answer.

IF... it's 4 sisters and 2 brothers, then we have
Ana and 3 other females
Andrew and 2 other males
Here, Ana would have 3 sisters AND 3 brothers, which matches what we were told. This MUST be the answer (7 total children).

Final Answer:
[Reveal] Spoiler:
D


GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Re: Ana is a girl and has the same number of brothers as sisters. Andrew   [#permalink] 06 Dec 2017, 14:50
Display posts from previous: Sort by

Ana is a girl and has the same number of brothers as sisters. Andrew

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.