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Re: xy-plane- Slope [#permalink]
02 Mar 2011, 18:25

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This is very tricky. E. Just guessing. well it cant be B since you need to define what is line r and what is line s. And information IMO is not sufficient.

Re: xy-plane- Slope [#permalink]
02 Mar 2011, 18:57

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line r: y=ax+b line s: g=bx+c is b<c? statement 1: intersection of r and s is negative or y<0 and ax+b=cx+d <=> (a-c)x=d-b x=(d-b)/(a-c) <0 we cant conclusion about this so insufficient statement2: the slope of r < the slop of s or a<c , we dont know about b and d thus insufficient, 1+2. (d-b)/(a-c)<0 so or d-b< o and a-C> o or (d-b)>o or (a-c)< o from statement 2 we know that a<c thus eliminate the condision that (d-b)<0 and (a-c)>0 so sufficient C

Re: xy-plane- Slope [#permalink]
02 Mar 2011, 19:47

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I came up with 2 cases.

Case 1 intercept(r) > intercept(s)

Case II intercept(r) < intercept(s)

I am not sure if they are considering the +/- or the modulus of intercept. In case it is magnitude (modulus) of the intercept the answer is E. But consider the sign of the intercept, the answer is C.

Re: xy-plane- Slope [#permalink]
03 Mar 2011, 02:03

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shuwa wrote:

diebeatsthegmat wrote:

line r: y=ax+b line s: g=bx+c is b<c? statement 1: intersection of r and s is negative or y<0 and ax+b=cx+d <=> (a-c)x=d-b x=(d-b)/(a-c) <0 we cant conclusion about this so insufficient statement2: the slope of r < the slop of s or a<c , we dont know about b and d thus insufficient, 1+2. (d-b)/(a-c)<0 so or d-b< o and a-C> o or (d-b)>o or (a-c)< o from statement 2 we know that a<c thus eliminate the condision that (d-b)<0 and (a-c)>0 so sufficient C

line r: y=ax+b line s: g=bx+c

I think

line r: y=ax1+b line s: g=bx2+c if line r: y=ax+b line s: g=bx+c

it means that 2 lines intersect together at a common point?

Shuwa - I think diebeatsthegmat has a typo in his solution when he defines the lines the first time line r: y=ax+b, line s: g=bx+c .

In reality, he has defined the line s as y= cx+d as can be seen in his calculation for statement 1.

Also, defining lines as y=ax+b and y= cx+d, does not imply that they intersect at the same point, it is just a general form of equation for any line that has a defined slope (a and c for two lines here) and a defined y intercept (b and d for lines here).

Re: xy-plane- Slope [#permalink]
03 Mar 2011, 02:07

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gmat1220 wrote:

I came up with 2 cases.

Case 1 intercept(r) > intercept(s)

Case II intercept(r) < intercept(s)

I am not sure if they are considering the +/- or the modulus of intercept. In case it is magnitude (modulus) of the intercept the answer is E. But consider the sign of the intercept, the answer is C.

Hope the helps!

The question simply asks if y intercept of r is less than y intercept of s, so we need to take the value of the intercept and not the absolute value.

A general line would be y=mx+c where y intercept is c which can be negative or positive or zero, so we need to just compare the actual value and that would involve incorporating the sign of the intercept as well.

I think diebeatsthegmat has the best approach to solve this without any confusion whatsoever.

Re: xy-plane- Slope [#permalink]
03 Mar 2011, 05:24

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Thanks beyondgmatscore. Yeah all ordered now. So I change this statement. Answer is C - whether you use visual approach or algebra.

beyondgmatscore wrote:

gmat1220 wrote:

I came up with 2 cases.

Case 1 intercept(r) > intercept(s) Case II intercept(r) > intercept(s)

I am not sure if they are considering the +/- or the modulus of intercept. In case it is magnitude (modulus) of the intercept the answer is E. But consider the sign of the intercept, the answer is C.

Hope the helps!

The question simply asks if y intercept of r is less than y intercept of s, so we need to take the value of the intercept and not the absolute value.

A general line would be y=mx+c where y intercept is c which can be negative or positive or zero, so we need to just compare the actual value and that would involve incorporating the sign of the intercept as well.

I think diebeatsthegmat has the best approach to solve this without any confusion whatsoever.

Re: xy-plane- Slope [#permalink]
04 Mar 2011, 11:18

I'm pretty sure I marked C without doing math on this, just drawing a few sketches knowing that:

I) the slopes can be anything, the intercepts can be anything, just that their points together are in Quadrant III (-x,-y); not sufficient

II) slope R is greater than slope S, just the steepness of the line, you can put the lines anywhere in the plane or any quadrant; not sufficient

Together, intercepting in Quadrant III and bigger slope? visually it just seems that it would have to hit higher all the time on the Intercept? am i wrong to think of it this way?
_________________

Re: xy-plane- Slope [#permalink]
05 Mar 2011, 06:59

beyondgmatscore wrote:

gmat1220 wrote:

I came up with 2 cases.

Case 1 intercept(r) > intercept(s)

Case II intercept(r) < intercept(s)

I am not sure if they are considering the +/- or the modulus of intercept. In case it is magnitude (modulus) of the intercept the answer is E. But consider the sign of the intercept, the answer is C.

Hope the helps!

The question simply asks if y intercept of r is less than y intercept of s, so we need to take the value of the intercept and not the absolute value.

A general line would be y=mx+c where y intercept is c which can be negative or positive or zero, so we need to just compare the actual value and that would involve incorporating the sign of the intercept as well.

I think diebeatsthegmat has the best approach to solve this without any confusion whatsoever.

yep, thats also correct in some cases, anyways i am a girl! i am a her, not a him lol

gmatclubot

Re: xy-plane- Slope
[#permalink]
05 Mar 2011, 06:59