Problem of the day – #1 Solution
If y is a positive integer > 1, which of the following can never have more unique prime factors than y?
I. y2
II. y11
III. 10y
(A) I and II (B) I and III (C) II and III (D) I, II, and III (E) III only
Solution:
If y is a positive integer > 1, yn will have the same number of unique prime factors as y. For example, if y = 3 and n = 2, then y2 = 32. Both 3 and 32 have one unique prime factor, which is 3. By the same reasoning, if n = 11 and y is still 3, both 3 and 311 have only 3 as the unique prime factor. In III, 10y may or may not have more unique prime factors than y. For example, if y = 3, then 10y = 30. The prime factorization of 30 is 3 x 2 x 5. There are three unique prime factors here. However, if y = 10, 10y = 10 x 10. The prime factorization of 10 x 10 = 5 x 5 x 2 x 2. There are only two unique prime factors here. Thus, only I and II can be correct.
Answer: A
Problem of the day – #1
If y is a positive integer > 1, which of the following can never have more unique prime factors than y?
I. y2
II. y11
III. 10y
(A) I and II (B) I and III (C) II and III (D) I, II, and III (E) III only
Practice Questions vs. Practice Tests
If you are taking the GMAT for the first or second time, you may be wondering how to best prepare for your exam. Every GMAT student with whom I have ever spoken has struggled with the best way to prepare for the GMAT. In five years as a GMAT tutor, I have never met a student who did not want to complete his preparation in as little time as possible. For this reason, many GMAT students are overly reliant on GMAT practice tests as the staple of their preparation. The theory behind this is to take as many practice tests as possible and then review only the topics addressed by their incorrect answers. This is an incomplete way to prepare for the GMAT and ultimately wastes valuable time and energy.
Let’s consider any GMAT computer adaptive practice test: 37 math questions and 41 verbal questions. The quantitative section consists of about 19 topics (http://www.targettestprep.com/currigmat.php). Therefore on any test you will see approximately 1.9 math questions per topic (37 questions divided by 19 topics). Since there are numerous ways in which a question from any particular topic can be presented, merely counting the number of topics incorrectly is an extremely imprecise way to gauge your weaknesses. For instance, let’s say you correctly answer a practice question testing you on average rate. Does this mean that you have a thorough understanding of all rate questions? Can you correctly answer a converging rate, a catch-up and pass rate, or a round trip rate question? Unless you further test your knowledge in that particular topic, you will never know!
If you have never taken a GMAT before, I do suggest completing a computer adaptive practice GMAT to get a base-line GMAT score. Then as you continue studying, you can compare future practice exam scores with old practice exam scores to ensure that you are moving in the right direction. Once you determine your base level, you can now move on to learn thoroughly each GMAT math topic. Gaining an in-depth knowledge of each individual topic takes a lot of patience. But it is crucial that you learn every topic in as complete a way as possible.
As an example, let’s again refer to rate problems. In the Rates Chapter of the Target Test Prep math guide there are 18 different sections with 24 different examples of rate problems. We include so many different examples because there are many ways in which these questions can be presented on the GMAT, and to achieve a top score, you need to be familiar with all of them! To ensure that you have truly learned a topic, challenge yourself with a great number of differing types of practice questions specifically from the topic you have just learned. The Rate Chapter of the Target Test Prep math guide includes 68 practice problems. Once you have successfully completed them, you can feel confident that you will be well prepared to successfully answer any rate question on test day.
This process is applicable to all GMAT topics, and this method will provide very few surprises (if any) when you take the real GMAT exam.
GMAT Time Traps
On the GMAT quantitative section, you are given 75 minutes to complete 37 math questions. On average, this gives you roughly two minutes per question; this is not a lot of time. In order to achieve a high GMAT score, efficient timing is critical. Many questions you see on the GMAT are designed to trap you into spending too much time to answer them. I call these questions “time traps”.
Most time trap questions appear easy and thus try to bait you into solving them using traditional math methods when there are significant shortcuts that can be taken using appropriate GMAT strategies. Because of the “easy” appearance of these questions, most GMAT test-takers will plod through endless traditional calculations regardless of how many attempts it takes or how much time it wastes. Sometimes these calculations will work; sometimes they’ll fail, but they will always waste precious time. The GMAC knows that it is not part of human nature to just give up on a problem, especially a problem that seems so simple! To further illustrate this, consider the following:
When you get a running start, the maximum height you can reach is 8 feet. Knowing this, if I were to hang a 100 dollar bill 8 feet, 1 inch off the ground, would you try and grab it? I’m pretty sure most of us would say yes! Because after all, how hard can it be to jump one inch higher.
The GMAT “time trap” questions attempt to trigger this thought process. Let’s consider the following example:
66 is equal to which of the following?
A) 46,522
B) 46,604
C) 46,656
D) 46,688
E) 46,720
When first looking at this question, it appears simple; we are asked to calculate 6 to the 6th power. If I were to use traditional math methods, I would solve it the following way:
Step 1) 62 = 6 x 6 = 36
Step 2) 63 x 36 x 6 = 216
Step 3) 64 = 216 x 6 = 1,296
Step 4) 65 = 1,296 x 6 = 7,776
Step 5) 66 = 7,776 x 6 = 46,656
After 5 steps involving tedious calculations, we arrive at the correct answer, 46,656. If you saw this question on the GMAT and solved it using the same method as described above, I envision two possible scenarios.
Scenario 1:
The best case scenario is that you answer the question correctly. When timed, many of my students are able (in non-GMAT conditions) to calculate 6 to the 6th power in around 1.5 to 2 minutes. However, taking this much time on such a straightforward problem may in fact hurt you later on in the test when confronted with more difficult problems. Had you saved time on this problem, you would now have time to spare. Without realizing it, you have fallen for a GMAT time trap.
Scenario 2:
The worst case scenario is that you try to solve this problem as above, but failing to arrive at the correct answer and knowing that this problem is “easy”, you try again! All of a sudden, you have spent four minutes on this one problem and have effectively put yourself into a timing hole so deep you can’t climb out. Once again, you have fallen for a GMAT time trap.
To avoid these traps, always consider GMAT strategies in solving GMAT problems. The strategy I would apply to the problem above relates patterns of unit digits. You would need to have learned that a base of 6 raised to any positive integer power will always have a unit digit of 6. Notice that out of the 5 answer choices, only one has a unit digit of 6, 46,656. Using this strategy, you could have correctly answered this question in about 10 seconds or less and thus avoided the dreaded time trap.
If you can carry this mindset into test day, you will be one step closer to GMAT success.
What you need to know about the new Integrated Reasoning Section
On June 5th, a new Integrated Reasoning Section will be added to the GMAT. The purpose of this new section is to enhance the ability of Business Schools to predict the academic performance of prospective candidates. You will have 30 minutes to complete 12 questions. The test as a whole will not increase in length, though, since one of the existing 30-minute essays will be dropped. Questions in this section will test your ability to extract and analyze information from different data sources such as graphs, tables, and various texts. It will be scored on its own separate scale and will not affect the overall numerical score of your GMAT exam.
How do I prepare for the Integrated Reasoning Section?
The good news is that you will not have to learn any new topics in order to successfully answer the questions. You simply need to practice these new question types until you become comfortable with them. The new 13th edition of the Official Guide to the GMAT has been released – it provides online access to 50 Integrated Reasoning practice questions. These will give you a feel for how these questions will be presented on the test.
What does all this mean for me?
Over the last few months, I have had many conversations with prospective GMAT students, who all share one concern: they want to take the GMAT before the change! When determining when to take your next GMAT, I would ask you the following question: If you take the GMAT before June will you be rushing the exam or be truly prepared to take it by that date? If the answer is yes, then it’s a no-brainer; take the exam. Otherwise, wait until you feel more confident.
When are Business Schools going to use this section?
Like the rest of the test, the Integrated Reasoning Section is designed to serve as a barometer of how well a potential business school student will fare in business school classes. In order to truly compare an Integrated Reasoning score with business school performance, business schools need sufficient data! It is going to take at least a few years to compile and analyze these results. Consequently, if you are applying in the next year, or even the next two years, your Integrated Reasoning score should not have a significant impact on your business school application. Analogously, an essay section was added to the SAT (Scholastic Assessment Test) in 2005. It was not until 2008, that the College Board, the makers of the SAT, published a comprehensive analysis of the correlation between the SAT essay section and student performance in college: SAT analysis. There is no reason to expect that the GMAC will not need a similar amount of time to compile enough data for a similar type of study.
Consider this as well. If you are applying to business school for the fall of 2013, you will be submitting your application within the next year. Most of the applicants for that session will not have taken the GMAT with the new Integrated Reasoning Section. Therefore, it will be impossible for them to use to this section in comparing all applicants.
At the end of the day, I suggest preparing for the GMAT as you normally would. If there is one thing that I have learned over the last 5 years as a full time GMAT tutor, rushing through your GMAT preparation will generally lead to poor performance on the test. So take your time, study hard, and take your GMAT when you’re ready.
Target Test Prep GMAT Success Story – Ryan
The 20 seconds of nervous anticipation that you feel after you click the submit button but before you receive your GMAT score ended in dread for me when I saw the number 610 staring back at me. My goal had been a 680, and I had failed miserably — even though I had taken a Kaplan course and had studied my butt off for the exam. So what happened? Who knew? One thing was certain: My dream of going to a top-ranked international program had disappeared behind the image of that 610.
As I continued to stare at the screen in numb disbelief, something else struck me, to my immediate embarrassment. I had scored in the 36% percentile in math! That’s right… that means that almost 65% of the people who took the exam scored better than I did in math. I knew math wasn’t my strong point, but little did I know how poorly prepared I was for GMAT math.
After months of trying to convince myself that maybe an MBA wasn’t right for me, I decided to give it one more shot. But this time, I wouldn’t take a class with 25 other people. I wanted personalized attention that would focus specifically on what I needed to improve upon. I met with the team at Target Test Prep and explained my story and what I was trying to accomplish. Based on our initial meeting, I felt they had my best interests in mind and would do a good job of helping me locate and root out my weaknesses. In other words, they would put me in the best possible position to succeed.
I was fortunate to have scored highly on the verbal section of the test the first time around, so I could concentrate solely on math. As a result of working with my GMAT tutor Jeff on a weekly basis, my quant scores began to improve. Soon, I was scoring in the 660 – 690 range on practice exams, and my confidence continued to increase as I became more and more familiar with the question formats and with the tricks used to hide those formats. I began to recognize what each question was really asking.
Finally, the big day was upon me. I had decided that this would be my final try at the exam; my future rode on my performance over the next few hours in the Pearson exam center. Finally, I clicked submit; the 20-second wait seemed to take forever. As I opened my eyes to peek at the screen, I was warmly greeted with the score of 680. I was ecstatic! Leaving the test center, I slapped the Pearson employee a huge high-five. I headed out into the cool fall air of New York City with a renewed sense of hope. “At least I have given myself a chance”, I thought to myself.
It’s months later as I write this, and as I prepare to be a first year MBA student at IESE Business School in Barcelona, Spain, I think back and realize that I wouldn’t be brushing up on my Spanish or preparing for a new stage in my life without the long hours of study and without the help of Jeff and his team.
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