line n and p lie in the xy plane, is the slope of line n

Question

line n and p lie in the xy plane, is the slope of line n less than the slope of line p?
(1) n and p intersects at point (5;1)
(2)y-intercept of line n is greater than y-intercept of line p

if possible, pls with explanation...
OA is C

GMATBLACKBELT · Answer

Slope is (Y2-Y1)/(X2-X1) 1: No help here at all. 2: No help again. Together: lets just pick a random point. (0,3) and (0,4) p and n respectively. (4-1)/(0-5) (3-1)/)(0-5) --> -3/5 < -2/5 (0-3) (0,-4) n and p respectively (-3-1)/(0-5) and (-4-1)/(0-5) --> 4/5 < 1 So suff.

pmenon · Answer

Dont follow your approach here, can you explain ?

sam76 · Answer

Let the lines be y = Nx +c1, y = Px + c2 where N and P are the slopes of lines n and p

from 1) Each of them passes thru (5,1)

1 = 5N + c1, 1 = 5P+c2
=> c1 = 1 - 5N, c2 = 1 - 5P....Not sufficient

from 2) c1 > c2 ...Not suffficient

Combining 1) & 2)
 1-5N>1-5P

=> P > N....Hence C

GK_Gmat · Answer

Stat 1: 
n could be || to x axis with slope 0 and p could be downward sloping, i.e., w/ slope -ve. Answer to step is no. 
p could be || to x axis w/ slope 0 and n could be downward sloping, i.e., w/ -ve slope. Answer to stem is yes.
Insuff.

Stat 2: 
n could intercept y axis at 5 and be || to p which intercepts the y axis at 2, in which case slopes are equal.
n could be downward sloping intersecting y axis at 5 and p could be upward sloping intersecting the y axis at 2. 
Insuff.

Together:
If n and p intersects at point (5,1) & y-intercept of line n is greater than y-intercept of line p then slope of n has to be less than slope of p. Suff.

sondenso · Answer

I like this, thanks

kbulse · Answer

thanks very detailed

GGUY · Answer

Guys, this is a correct answer of course but in my opinion it takes too much time to solve it algebrally.

(1) I would draw the x-y plain, put the (5,1) point on it and draw 2 straight lines. they can be drawn all over the plain.insuff

(2) again, on the same x-y plain I draw two points intersecting the y axis, (n,0) point is higher than (p,0) point. insuff.

draw 2 stright lines from (n,o) to (5,1) and from (p,0) to (5,1) and see that the the lines can not be drawn diffrently. slope has to be different.suff

took me less than a minute. I think that in this case it works better for me

bsjames2 · Answer

1) We know the intersection point, but we don't know anything else - INSUFFICIENT
2) We know the y-intercepts, but this doesn't tell us anything about the slope

TOGETHER
Since the y-intercept of n is greater than p, we know that n's slope must be less than p, otherwise they wouldn't intersect.

line n and p lie in the xy plane, is the slope of line n

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