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by Rich Cohen, EMPOWERgmat.com; [email protected]
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.
Complex Math vs. Easier Approaches in the Quant Section
Rich,
How often will I see complex exponent questions like this on the GMAT:
If 4^a + 4^a+1 = 4^a+2 - 176, what is the value of a?
1
2
3
4
5
How much time should I spend learning to do this type of math?
Smithers
Hi Smithers,
While there are several ways to approach this type of question, I'd like to reiterate that the GMAT will rarely require that you do complex math to answer a given Quant question. As such, there is almost always another way to get the solution that will involve easier ‘work.’ Here, using the answers to your advantage can help you to solve this type of question relatively quickly.
We know that 4^a, 4^(a+1) and 4^(a+2) are three consecutive "powers of 4", so we could just "map out” the possibilities and find the option that fits the given equation.
4^0 = 1
4^1 = 4
4^2 = 16
4^3 = 64
4^4 = 256
4^5 = 1024
Now, which 3 consecutive "powers of 4" fit the given equation (hint: the "-176" is a specific value)?
It's got to be 2, 3 and 4….
4^2 + 4^3 = 4^4 – 176
16 + 64 = 256 – 176
80 = 80
…so a = 2. Notice how all I really did was some basic arithmetic to get to the solution. Keep a flexible mind and realize that learning how to do complex math is not a requirement to earn a high Quant Scaled Score on Test Day.
Advice with 15 Days to Go and Scoring in the High 600s
Dear Rich,
Please can you suggest what my strategy should be for the next 15 days – I’m trying to raise my score from 680 on my last mock to 730. I really really really want to improve my score and I understand that a 50 point improvement in 15 days isn't going to be easy. I have planned to do a series of 5 mocks before my actual exam, but apart from that what kind of questions should I focus on?
Travis
Hi Travis,
With a 680, you’re already scoring at a really high level overall, so you’ll have to nit-pick your performance when you review this CAT. What types of questions were you getting wrong and WHY. With only 15 days to go, you should be focused on honing your ‘precision’ – eliminating little mistakes, taking better notes, NOT doing work ‘in your head’, etc. You’d be amazed how quickly and easily you can pick up points once you remove the little errors from your work.
Your plan to take 5 CATs in 2 weeks is a TERRIBLE IDEA. You should plan to take 1 CAT/week at most (and be sure to take the ENTIRE CAT) and spend the rest of your time studying. Taking lots of CATs in a short period of time will NOT make you a better Test Taker.
The Reality of Answer A in Sentence Corrections
Hi Rich,
I am working on SC practice and have noticed that many answer choices in certain practice materials are A. If A is not eliminated off the bat, and I am stuck with a second choice, is it better for my odds to just choose A?
Ulysses
Hi Ulysses,
The GMAT tends to evenly distribute the answer choices throughout each section during the exam. As such, answer A will be correct about 20% of the time (since there are 5 answer choices to each question). Since you’re going to see approximately 15 SCs on Test Day, it stands to reason that about 3 of them would be fine the way that they're written. This doesn't necessarily mean that you have "better odds" by picking A, but you do have to be comfortable with the idea that there might not be any errors in the original sentence.
GMAT assassins aren't born, they're made,
Rich
