178 Does straight line have a negative slope?

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ern5231: Master | Next Rank: 500 Posts; Posts: 226; Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Wed Oct 07, 2009 5:19 pm

In rectangular coordinate system, a straight line has a point (c,d) in the first quadrant. Does the line have a negative slope?
1) the straight line also crosses (c+2, d-3)
2) this straight line's x-intercept is greater than y-intercept

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sunnyjohn: Master | Next Rank: 500 Posts; Posts: 344; Joined: Mon Sep 14, 2009 5:40 amFollowed by: 3 members; Thanked: 28 times; GMAT Score:700

by sunnyjohn » Wed Oct 07, 2009 6:22 pm

IMO:D

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crackgmat007: Legendary Member; Posts: 882; Joined: Fri Feb 20, 2009 2:57 pmFollowed by: 1 member; Thanked: 15 times; GMAT Score:690

by crackgmat007 » Wed Oct 07, 2009 9:38 pm

By POE, I could get it to C or E. I would guess E.

1. Gives many possibilities
2. Picking numbers, if X intercept is 4 & Y is 3, line has a negative slope. If Y is -3, line has a positive slope.

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rohittk: Junior | Next Rank: 30 Posts; Posts: 27; Joined: Thu Jun 04, 2009 11:05 am; Thanked: 2 times; GMAT Score:670

by rohittk » Thu Oct 08, 2009 1:56 am

Answer is D as slope = (y2 - y1)/ (x2 - x1).
Interpolate values into this equation and you know why the answer is D.

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ershovici: Senior | Next Rank: 100 Posts; Posts: 91; Joined: Tue Aug 25, 2009 7:50 am; Location: Washington DC; Thanked: 2 times; GMAT Score:600

by ershovici » Thu Oct 08, 2009 3:27 am

I think the answer is A.
Just drow a scetch and you will see that the line which passes through these two points can not have positive slope.

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crackgmat007: Legendary Member; Posts: 882; Joined: Fri Feb 20, 2009 2:57 pmFollowed by: 1 member; Thanked: 15 times; GMAT Score:690

by crackgmat007 » Fri Oct 09, 2009 7:34 am

rohittk wrote:Answer is D as slope = (y2 - y1)/ (x2 - x1).
Interpolate values into this equation and you know why the answer is D.

Can you explain how B is sufficient?

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

Re: 178 Does straight line have a negative slope?

by Brent@GMATPrepNow » Fri Oct 09, 2009 10:42 am

ern5231 wrote:In rectangular coordinate system, a straight line has a point (c,d) in the first quadrant. Does the line have a negative slope?
1) the straight line also crosses (c+2, d-3)
2) this straight line's x-intercept is greater than y-intercept

(1) If the line passes through (c,d) and (c+2, d-3), we can apply the slope formula to see that the slope is -3/2 --> SUFF

(2) INSUFF
Case a) x-intercept=6, y-intercept=1 --> negative slope
Case b) x-intercept=6, y-intercept=-1 --> positive slope

Brent Hanneson - Creator of GMATPrepNow.com

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