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Gmat Prep question 2

by msd_2008 » Tue Jul 22, 2008 11:42 pm
Q. In the xy plane, what is the y intercept of Line L

1. The slope of line L is 3 times its y intercept

2. the x intercept of line L is -1/3
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by pepeprepa » Wed Jul 23, 2008 2:39 am
Would say E. Is it the answer?
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by Canman » Wed Jul 23, 2008 12:39 pm
I think it is E

1) Y=3m(x)+m - doesn't allow us to conclude one value for m. - INSUFFICIENT

2) no slope given - INSUFFICIENT

Together statement 2) doesn't provide incremental information (see below) to statement 1, still insufficient.

If we look for X intercept using just statement 1) we find:
0=3mx+m
x=-1/3

So no new information with statement 2
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by wilderness » Wed Jul 23, 2008 1:55 pm
What if we were given explicity that the slope is positive (or that its negative)

Would that be of any help ?
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by Canman » Wed Jul 23, 2008 3:02 pm
I don't think knowing just the sign alone would help. If I understand the problem correctly we need the direction and the magnitude to help us extrapolate the Y intercept based on the information provided in statement 1.

As for statement 2, knowing the direction alone still provides an infinite number of possibilities for lines that we can draw from an x-intercept of -1/3.
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by microke » Wed Jul 23, 2008 11:00 pm
I think the answer is C...

From statement 1 y=3m(x)+m
From statement 2 x=-1/3

So y=-m+m =o; hence y=0 means it is the x axis itself....x axis has got a slope of zero...Hence answer C
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by pepeprepa » Thu Jul 24, 2008 12:54 am
There is an infinity of lines.
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by Canman » Thu Jul 24, 2008 3:24 am
Microke-

I don't think x=-1/3 and x-intercept = -1/3 are equivalent statements. So I'm not clear on the substitution. Am I wrong on this?
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by microke » Thu Jul 24, 2008 3:45 am
Canman, I think one can assume x intercept as the point crossing x axis , that is at x=-1/3 when the assumed straight line is of form y=mx+c... I am also not so confident, what is the OA?
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