Lesson: Intro to GRE Quantitative Comparison (QC)

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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.

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

Thanks Shahbaz!

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?

Cheers,
Brent

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?

Cheers,
Brent