GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Jul 2018, 01:05

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

Does the line with equation ax + by = c, where a, b and c are real con

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

Hide Tags

Intern
Intern
avatar
Joined: 25 Apr 2015
Posts: 4
GMAT ToolKit User
Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 04 May 2016, 10:18
11
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

65% (00:55) correct 35% (01:44) wrong based on 237 sessions

HideShow timer Statistics

Does the line with equation ax + by = c, where a, b and c are real constants, cross the x-axis?

(1) b ≠ 0
(2) ab > 0

Hi guys!

I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:

Here is my solution: I solved the equation for y, so that I got y=-ax/b + c/b. If the line crosses the x-axis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b
Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E.
However, this is not the official answer ...
2 KUDOS received
Intern
Intern
avatar
Joined: 01 Jan 2015
Posts: 31
Location: India
GPA: 3.71
WE: Consulting (Retail Banking)
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 04 May 2016, 10:36
2
1
if b is not equal to zero then if a equal to zero then it will definitely not pass by x axis where as when a is non zero may pass so 1st statement is not sufficient.
if ab>0 the either both are positive or both are negative also non of them as zero. Hench there will always be ax+by hence always a slope(-a/b) and if a line always has slope it will always pass through x axis. So the answer can be given only by statement 2 hence B is the answer.
_________________

_________________
"Kudos please :)"

Intern
Intern
avatar
Joined: 05 May 2016
Posts: 2
Location: Israel
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 05 May 2016, 12:09
aishkar wrote:
if b is not equal to zero then if a equal to zero then it will definitely not pass by x axis where as when a is non zero may pass so 1st statement is not sufficient.
if ab>0 the either both are positive or both are negative also non of them as zero. Hench there will always be ax+by hence always a slope(-a/b) and if a line always has slope it will always pass through x axis. So the answer can be given only by statement 2 hence B is the answer.


Fix me if i'm wrong:
Generally, we can say that if b=0, then the slope is infinite and will definitely cross the x axis (straight vertical line).
Also we can say that if -ax+c=0 the line will never pass through the x axis (straight horizontal line).

Am i right about that subject?
_________________

IMPOSSIBLE IS NOTHING!

Manager
Manager
avatar
Joined: 17 Sep 2015
Posts: 95
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 08 May 2016, 21:00
by = -ax + c

y = -(a/b)*x + c/b

if x = 0, then y = c/b

and if y = 0, then

(a/b)*x = c/b

x = c/a........., we need a!= 0

this is valid only in B) Hence B is the ans.....can someone confirm this?
_________________

You have to dig deep and find out what it takes to reshuffle the cards life dealt you

1 KUDOS received
Manager
Manager
User avatar
Joined: 18 May 2016
Posts: 67
Concentration: Finance, International Business
GMAT 1: 720 Q49 V39
GPA: 3.7
WE: Analyst (Investment Banking)
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 06 Jun 2016, 11:25
1
aniketm.87@gmail.com wrote:
by = -ax + c

y = -(a/b)*x + c/b

if x = 0, then y = c/b

and if y = 0, then

(a/b)*x = c/b

x = c/a........., we need a!= 0

this is valid only in B) Hence B is the ans.....can someone confirm this?


I am wasn't sure what you meant in the last line with a!=0

My thinking for the last line following your method:

We know that x = \(\frac{c}{a}\)

The question is asking us: Is there a value x for when y equals 0? The only circumstance when x = \(\frac{c}{a}\) will not have an actual value is if a = 0,then the answer is undefined and there is not value of x for when y = 0.

Thus, Stem 2 tells us that a*b > 0, which means they are both positive or negative and thus, there will always be a value of x when y = 0.

Hope it helps!
_________________

Please kindly +Kudos if my posts or questions help you!

My debrief: Self-study: How to improve from 620(Q39,V36) to 720(Q49,V39) in 25 days!

Senior Manager
Senior Manager
avatar
Joined: 02 Mar 2012
Posts: 334
Schools: Schulich '16
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 07 Jun 2016, 01:03
B

to NOT cross x axis constant a=0

1)nothing about a is given . a=0 or a is not eq to 0

2)ab>0 a,b =+ve or a,b+-ve but surely not 0. that means line can have either +ve or -ve slope.
Suff


hope it helps
4 KUDOS received
Retired Moderator
User avatar
B
Joined: 05 Jul 2006
Posts: 1734
GMAT ToolKit User Premium Member
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 07 Oct 2016, 08:34
4
dgeorgie wrote:
Hi guys!

I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:

Does the line with equation ax+by=c, where a,b and c are real constants, cross the x-axis?
(1) b ≠ 0
(2) ab>0

Here is my solution: I solved the equation for y, so that I got y=-ax/b + c/b. If the line crosses the x-axis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b
Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E.
However, this is not the official answer ...



the question asks whether the line is parallel to x axis or not

slope = -a/b if = 0 then line is parallel if not then it definitely crosses the x axis

from1 ...no idea about a .... insuff

from 2

neither a nor b is 0 and they have the same sign thus slope is -ve and ll defo cross the x axis

B
Intern
Intern
avatar
B
Joined: 30 May 2017
Posts: 41
Re: Does the line with equation ax + by = c, where a, b and c are real con  [#permalink]

Show Tags

New post 13 Jan 2018, 02:57
I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:

Does the line with equation ax+by=c, where a,b and c are real constants, cross the x-axis?
(1) b ≠ 0
(2) ab>0

Here is my solution: I solved the equation for y, so that I got y=-ax/b + c/b. If the line crosses the x-axis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b
Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E.
However, this is not the official answer ...


Hi,

If the line crosses x axis then there must be a point (x,0) not (0,y) as assumed by you.
Re: Does the line with equation ax + by = c, where a, b and c are real con &nbs [#permalink] 13 Jan 2018, 02:57
Display posts from previous: Sort by

Does the line with equation ax + by = c, where a, b and c are real con

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

Events & Promotions

PREV
NEXT


cron

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.