In the xy plane what is the Y intercept of line L
(i) The slope of line l is 3 times its Y intercept
(ii) The x intercept of line l is -1/3.
Pl help me solve this.
Y Intercept Of Line
This topic has expert replies
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
(1) Lots of possible linesSumit69 wrote:In the xy plane what is the Y intercept of line L
(i) The slope of line l is 3 times its Y intercept
(ii) The x intercept of line l is -1/3.
Pl help me solve this.
(2) Lots of possible lines
Note: If we draw any (non-vertical) line through the point (-1/3, 0) [aka the x-intercept) the slope of the line will be three times its y-intercept.
Choose any point on the y-axis and determine the slope between this point (-1/3, 0). You'll see that when you divide by the rise (the y-intercept) by the run (1/3), you are essentially muliplying the y-intercept by 3.
I've attached a graphic with 2 possible lines, but there are many (infinitely) more.
-
- Senior | Next Rank: 100 Posts
- Posts: 33
- Joined: Thu Feb 19, 2009 7:19 pm
- Location: DC
- Thanked: 2 times
y=mx+b
Question: What is b?
1) m=3b - insufficient
2) x intercept =-1/3 - y intercept could be positive or negative depending on the slope of the line. Insufficient.
Together: we have a point x intercept (-1/3,0), plug it into the y=mx+b equation:
0=m(-1/3)+b
Using stmt 1--> 0=3b(-1/3)+b - we can solve for b. Sufficient.
Ans is C.
Question: What is b?
1) m=3b - insufficient
2) x intercept =-1/3 - y intercept could be positive or negative depending on the slope of the line. Insufficient.
Together: we have a point x intercept (-1/3,0), plug it into the y=mx+b equation:
0=m(-1/3)+b
Using stmt 1--> 0=3b(-1/3)+b - we can solve for b. Sufficient.
Ans is C.
-
- Junior | Next Rank: 30 Posts
- Posts: 26
- Joined: Tue Oct 21, 2008 12:10 pm
- Thanked: 3 times
- GMAT Score:770
This did not solve for b since b just fell out and you're left with 0=0. What exactly is b? While unnecessary to solve for the answer in DS problems, solving for it is the definition of a proof. That can't be done here. The answer is E.iwant700plus wrote: Using stmt 1--> 0=3b(-1/3)+b - we can solve for b. Sufficient.
Ans is C.
-
- Senior | Next Rank: 100 Posts
- Posts: 33
- Joined: Thu Feb 19, 2009 7:19 pm
- Location: DC
- Thanked: 2 times
You are right. Thanks for catching that!
cm47323 wrote:This did not solve for b since b just fell out and you're left with 0=0. What exactly is b? While unnecessary to solve for the answer in DS problems, solving for it is the definition of a proof. That can't be done here. The answer is E.iwant700plus wrote: Using stmt 1--> 0=3b(-1/3)+b - we can solve for b. Sufficient.
Ans is C.
-
- Junior | Next Rank: 30 Posts
- Posts: 16
- Joined: Tue Jan 06, 2009 1:07 pm
iwant700plus was dead on in the equation but he set the equation equal to 0. it should be y = 3b(-1/3) + b (taking S1 and S2 together of course). so y = 0 (which is ends up being the y-intercept). please correct me if i am wrong?