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Lines and Slopes

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by vineeshp » Thu May 12, 2011 6:57 am
Lines n and p lie in the xy-plane. Is the slope of line n less than the slope of line p ?

(1) Lines n and p intersect at the point (5,1).
(2) The y-intercept of line n is greater than the y-intercept of line p.

OA is C
Vineesh,
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Source: — Data Sufficiency |

by GMATGuruNY » Thu May 12, 2011 7:45 am
vineeshp wrote:Lines n and p lie in the xy-plane. Is the slope of line n less than the slope of line p ?

(1) Lines n and p intersect at the point (5,1).
(2) The y-intercept of line n is greater than the y-intercept of line p.

OA is C
Statement 1: Lines n and p intersect at the point (5,1).
No way to determine whether the slope of line n is less than the slope of line p.
Insufficient.

Statement 2: The y-intercept of line n is greater than the y-intercept of line p.
No way to determine whether the slope of line n is less than the slope of line p.
Insufficient.

Statements 1 and 2 combined:
Slope = (y2 - y1)/(x2 - x1).
Given the y-intercept (0,y1) and the point (5,1):
For each line, the denominator of the slope formula = x2 - x1 = 5-0 = 5.
Statement 2 indicates that the y-intercept of line n is greater than the y-intercept of line p.
Since the value of y1 is greater for line n, the value of 1-y1 (the numerator of the slope formula) will be less for line n than for line p, giving line p the greater slope.
Sufficient.

The correct answer is C.
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by MAAJ » Thu May 12, 2011 8:28 am
Edit: There is a typo in my post/images, line p should be n and viceversa. Slope of p will always be greater than the slope of n

It's a lot easier if you graph. Slope of n will always be greater than the slope of p.

Image

Image
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