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arijitpal2009
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Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by arijitpal2009 Thu Jul 24, 2014 9:20 pm

In page 217 of the second edition of geometry, i.e in the hard practice question no. 19, I am having a confusion.

Q In the x-y plane, line n is a line that passes through the origin. Which of the following statements individually provide(s) sufficient information to determine whether the slope of line n is greater than 1? Indicate all such statements

a) Line n does not pass through any point (a,b) where a and b are positive and a>b

b) Line m is perpendicular to n and has a slope of -1

c)Line n passes through the point (c, d+1) where c and d are consecutive integers and c>d


In the solution, it is given B and C are correct. But both these options point out the fact that the slope of the line is 1, not greater than 1, which is required as per question! Please give your opinion on this and give me a solution.
tommywallach
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Re: Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by tommywallach Fri Jul 25, 2014 1:13 pm

Hey Arjit,

Your understanding of the math here is great, but you're missing how the logic works.

In order for a piece of information to be sufficient to answer a question, the information needs to provide a definitive yes OR no. For example:

Are the following pieces of information sufficient for determining whether I live in France?

1. Tommy lives in Paris.
2. Tommy lives in Iceland.
3. Tommy lives in Europe.

1. This is sufficient. I can definitively say that Tommy lives in Paris.

2. This is also sufficient. I can definitively say that Tommy does not live in Paris.

3. This is insufficient. I don't know if Tommy does or does not live in Paris.

In the case of this question, if we know that the slope of the line in question is 1, we can definitively state that the slope is not greater than 1.

Hope that helps!

-t
arijitpal2009
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Re: Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by arijitpal2009 Thu Jul 31, 2014 11:35 pm

Thanks :) The logic can be sometimes confusing :p
tommywallach
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Re: Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by tommywallach Fri Aug 01, 2014 10:40 pm

Totally. I'm only good at it because the GMAT has a whole question type based around this type of logic!

-t
Videoorchard
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Re: Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by Videoorchard Wed Jun 03, 2015 12:59 am

Hello Tommy,

Thank you for clarifying the anwers! :) I have a doubt regarding the way the question is framed. its kind of confusing. The question states which of the following statements individually provide(s) sufficient additional information to determine whether the slope of line n is greater than 1? Doesnot this mean, okay, find all the options which supports the statement of slope being greater than 1? I am pretty sure, i will use the same exact wrong reasoning on the test day. How do you avoid falling into such logical fallacy?

Source:
Pg 225,
Question 19, (Hard practise Test)
Manhattan Strategy guide, Geometry.
tommywallach
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Re: Geometry 2nd edition (MGRE) geometry pg 217 question no-19.

by tommywallach Tue Jun 09, 2015 6:53 pm

Hey Video,

Not sure what to tell you. Something is only sufficient to answer the question if it allows you to answer the question. It's logical enough; it just might not be how you're used to thinking. Read over the explanation I gave a bunch of times. That should clarify it.

-t