Lesson: Intro to GRE Quantitative Comparison (QC)

Comment on Intro to GRE Quantitative Comparison (QC)

I'm very relieved to have found this course. It's like a healthy shot of WD40 working on the rust in my math-brain. Thank you very much!
greenlight-admin's picture

I'm glad you like it!

The best set of online resources for GRE i have come across till date . It's a 5/5 for the content , would recommend to all :)
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tahmina.mm's picture

I am so glad, i found this.


i cannot hear any thing on greenlighttestprep.com.. it was fine until an hour back. any setting? youtube greenlighttestprep and other videos sound ok
greenlight-admin's picture

I'm sorry to hear that you're having difficulties. I just checked several videos (including this one), and the volume works. I also checked with Vimeo (our video host), and no widespread problems have been reported.

Please clear the cache of your Web browser, then restart your computer and see if that resolves the issue? Also, can you try another Web browser and see what happens?

Here are the instructions for clearing your cache: https://kb.iu.edu/d/ahic (Note: you need not clear your cookies or your browsing history)

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UPDATE: franky_f reported that the problem was resolved once she cleared her cache

when i solved many QC problem, literally if found no question having E as answer? is it very rare in actual GRE?
greenlight-admin's picture

Quantitative Comparison question have only 4 answer choices:

A) The quantity in Column A is greater.
B) The quantity in Column B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.

So, E can never be the correct answer of a Quantitative Comparison question.

My blunder sorry! i was suppose to say D.
greenlight-admin's picture

I wouldn't say that it's rare for the correct answer to be D on an Quantitative Comparison question.

How is it possible that x= -5? -5^2 does not equal to a positive 25. I know i'm missing a step here, can someone explain this to me?
greenlight-admin's picture

Hi Ruby,

You're referring to the question that appears at 3:20 in the video.

The given information tells us that x² = 25

x = 5 is one solution, since 5² = (5)(5) = 25

x = -5 is another solution, since (-5)² = (-5)(-5) = 25

For more on multiplying positive and negative numbers, see the following video: https://www.greenlighttestprep.com/module/gre-arithmetic/video/1059

its really a relevant effort made by greenlighttestprep. its the only one, i can say, all in one regarding GRE preparation. excellent work is done and quality is there.
greenlight-admin's picture

Thanks Shahbaz!

In the question where the heights of Glen and Kayla are involved they didn't mention that Glen height is always <= 70 it can be >70 too in that case the correct option is 'D' and sorry if my interpretation is wrong.
greenlight-admin's picture

Hi Suhas,

You're referring to the question that starts at 2:10 in the above video.

The key here is that their heights add to 140 inches AND Kyla is taller than Glen.

For example, Kyla could be 72 inches tall, and Glen could be 68 inches tall.

Or Kyla could be 70.5 inches tall, and Glen could be 69.5 inches tall.

Or many other scenarios.

Now let's say for a moment that Kyla is 67 inches tall. This means Glen is 73 inches tall (to get a sum of 140 inches). HOWEVER, this does not meet the condition that Kyla is taller than Glen. So, it CANNOT be the case that Kyla is 67 inches tall.

Try finding some other values for their heights, and you'll find that Kyle will ALWAYS be more than 68 inches tall. In fact, she will always be taller than 70 inches.

Does that help?


Hi Brent,

I am further along the course but somehow ended up on this page again. In a later lesson, you mentioned that GRE only cares about the positive values for square roots. For example, sq rt of 25 = + 5 and - 5, however, since GRE only cares about the positive value (+ 5), won't the answer for the last example in this video be A? Please let me know. Thanks.
greenlight-admin's picture

You're referring to the question at 3:20 in the video.

Keep in mind that the original question does not have any square root signs.

The square root NOTATION tells us to take the POSITIVE square root of a number.
So, for example, √9 = 3, √25 = 5 and √49 = 7

Conversely, the equation x² = 25 does not feature any square root notation.
In this case, there are TWO SOLUTIONS: x = 5 and x = -5

If we want to formalize this outcome we can write:
If x² = k, then there are two possible solutions: x = √k and x = -√k

Does that help?


Yup, that cleared things up. Thank you!

If i start my prepration from now so how much time i have to give daily to complete the complete course in 3 months and 6 months respectively.
with this i will be able to plan my day with the time i have to give to the studies of GRE and my other collage exams.
And one more thing i am not a native English speaker i don't speak English that often and my vocabulary is poor how do i improve it and how do i memorize the GRE words.

Hope to hear from you soon.
greenlight-admin's picture

The course has about 220 video LESSONS, and about 280 video practice questions.
So, if you want to complete the entire course in X days, then the number of video LESSONS you should complete each day = 220/x

To do well on the GRE, you'll need to build a strong vocabularty.
This video will help with that: https://www.greenlighttestprep.com/module/gre-sentence-equivalence/video...

Does that help?


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