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by Rich Cohen, [email protected] www.EMPOWERgmat.com
This series of emails and PMs focuses on situations that many Test Takers face during their studies. The names of the original posters have been changed to protect their identities.
Absolute Values in DS Questions
Dear Rich,
In this DS, I get that from common sense we can consider p = q = 0, but if this did not strike one's mind instantly, then one can use the absolute value equation.
If I use this here, I get 2 values either p =-q or p = q
If above is the case, then I get either p+q= 0 or, p+q=2p or 2q
This is confusing. Can you please tell me what I am missing here?
What is the value of p+q?
(1) |p|= -|q|
(2) p=q
Zeb
Hi Zeb,
Your "math" explanation is too complicated for the given scenario (even you're not sure what it means, which is problematic) and takes more time to use than other approaches. The Quant section of the GMAT is NOT a math test, it's a critical thinking test that uses math as the "gauge." You should remember that fact when approaching Quant questions; there's usually several approaches to answering the given question (the "math way" often takes the longest though).
DS questions are often built around Number Properties (patterns behind the math and how numbers relate to one another). In Fact 1, since you know the definition of absolute value, your instinct should be to do the easiest thing that you can: a minus sign in front of an absolute value means the resulting value is either negative or 0. The ‘left side’ of that equation creates either a 0 or positive result. Since the two terms are equal, the only possibility is 0.
Work to build up that skill (especially on DS questions) and you'd be amazed how your score can quickly improve and any pacing problem that you may have could disappear.
Causality in CR
Hi Rich,
What is the logic in this CR question?
Two centuries ago, Tufe Peninsula became separated from the mainland, isolating on the newly formed Tufe Island a population of Turfil sunflowers. This population’s descendants grow to be, on average, 40 centimeters shorter than Turfil sunflowers found on the mainland. Tufe Island is significantly drier than Tufe Peninsula was. So the current average height of Tufe’s Turfil sunflowers is undoubtedly at least partially attributable to changes in Tufe’s environmental conditions.
Which of the following is an assumption on which the argument depends?
(A) There are no types of vegetation on Tufe Island that are known to benefit from dry conditions.
(B) There were about as many Turfil sunflowers on Tufe Peninsula two centuries ago as there are on Tufe Island today.
(C) The mainland’s environment has not changed in ways that have resulted in Turfil sunflowers on the mainland growing to be 40 centimeters taller than they did two centuries ago.
(D) The soil on Tufe Island, unlike that on the mainland, lacks important nutrients that help Turfil sunflowers survive and grow tall in a dry environment.
(E) The 40-centimeter height difference between the Turfil sunflowers on Tufe Island and those on the mainland is the only difference between the two populations.
Arnaud
Hi Arnaud,
This CR prompt is built on the concept of "causality", meaning that one thing causes another. It's a type of logic that you'll see a few times on Test Day, so it's worth knowing. The big assumption with causality prompts is that first thing (and NOTHING ELSE) caused the second thing.
Here, we're told that the change in environment conditions (the Island is drier than the Peninsula) caused the Turfil sunflowers to be 40 cm shorter than mainland sunflowers. We're looking for an answer that confirms that the dryness is the only possible cause (and nothing else).
The only answer that confirms the causality is C, which tells us that the difference in the height of the sunflowers was NOT due to something that happened on the mainland.
Balancing Subjects During Your Studies
Rich,
After a 6 month hiatus I'm back at it, and have made up my mind to write the test. I studied for almost 3 months straight last year, but never wrote the actual test because I didn't feel my score was good enough. My 3 month plan is to focus on Quant for the first month, then Verbal for the second month and work on CATs in the third month.
Any thoughts? Would really appreciate the feedback of the community, thanks.
Baker
Hi Baker,
Your plan might work just fine, although you’ll likely perform better overall if you do a ‘mix’ of Quant and Verbal each week (that way you can build up skills in BOTH sections of the Test at the same time. It’s also important to take CATs at regular intervals – if you don’t want to take a CAT every week, then that’s fine, but you shouldn’t wait until the end of your timeline to take them.
GMAT assassins aren't born, they're made,
Rich
