Yesterday, we posted a 700+ level GMAT question. Below is the answer and explanation. How’d you do?
ANSWER: C
This is the only advanced algebra you’ll need on the test. It’s not the only way to solve it, but it’s the easiest way to solve it.
To find a maximum or minimum value of an equation with an exponent in it, you take the derivative of the equation, set it to zero, and solve. That’s the max or min.
In this case we are given
P = -25x2 + 7500x
To find the derivative, multiply each number by the exponent it’s connected to, and subtract the exponent by 1. Here, that will look like:
P’ = -50x + 7500
Set P’ to zero, and solve:
0 = -50x + 7500
50x = 7500
x = 150
If you’re not sure this really worked, try plugging in numbers, or even running the original equation in Excel. You will see that at x = 150, P is the maximum it can be.
July 30th, 2008
Every Tuesday we post a 700+ level GMAT question here on our blog, and post the answer and explanation the following day. Do you have what it takes?
In a certain company, the formula for maximizing profits is P = -25x2 + 7500x, where P is profit and x is the number of machines the company operates in its factory. What value for x will maximize P?
A) 10
B) 50
C) 150
D) 200
E) 300
July 29th, 2008
Yesterday, we posted a 700+ level GMAT question. Below is the answer and explanation. How’d you do?
Answer: C
The sum of three integers is even – they can’t all be odd so the product will be even and B and D are eliminated.
To go further we must actually work.
Let’s make the mode be x. If it is a mode and there are three integers it must appear twice. Hence our three numbers are x-13 (the smallest), x and x.
x + x + (x – 13) = 50
3x – 13 = 50
x = 21
8*21*21 =
8*441 = 3,528
July 23rd, 2008
Every Tuesday we post a 700+ level GMAT question here on our blog, and post the answer and explanation the following day. Do you have what it takes?
The sum of 3 integers is 50. The smallest integer is 13 less than the mode. What is the product of the three integers?
A) 1,108
B) 2,041
C) 3,528
D) 4,111
E) 5,012
July 22nd, 2008
Yesterday, we posted a 700+ level GMAT question. Below is the answer and explanation. How’d you do?
Answer: A
K and M are positive so K+M must be at least 2 (B and D are eliminated).
Now for the tricky part: If one of the remainders is even then the other remainder must be even. If one of the remainders is odd, the other remainder must also be odd.
For example:
If J = 13, K is 1 and M is 1
If J = 9, K is 3 and M is 1
If J = 10, K is 4 and M is 2
The logic here (which we prefer you learn rather than plugging in numbers) follows: The remainder represents how far the number you are dividing is from the last multiple of the number you are dividing by. Since both 4 and 6 are even, their multiples will always be even. Since the rules for subtracting evens and odds are constant, whatever J is (even or odd), the distance it is from an even number will always be correspondingly even or odd.
Now, since either way the sum of K and M must be even (even + even is even; odd plus odd is even), there are no even values other than 0 and so the answer is none (A).
July 16th, 2008
Every Tuesday we post a 700+ level GMAT question here on our blog, and post the answer and explanation the following day. Do you have what it takes?
J, K and M are positive integers. K is the remainder when J is divided by 6. M is the remainder when J is divided by 4. Which of the following could be the value of K+M?
I. 0
II. 3
III. 9
A) None
B) I
C) II
D) I and III
E) II and III
July 15th, 2008
We continue with our series called “Wait It Out,” where we address many of the issues facing people thinking about business school in the current climate. Check back often as you contemplate your own business school choice!
We have talked a bit in previous posts about the effect of the economy on business school. But it looks like the Wall Street refugees aren’t the only folks contributing to the increase in b-school applications; we now have an increase in international students seeking out spots in MBA programs here in the US.
The reason for the increase? In a blog post this week, our friends at MBA Mission highlighted this other interesting factor affecting business school applications: the weakened US dollar. They noted an article from the Financial Times – “Falling Dollar Draws Students” – which discusses how the low US dollar is making American business school programs more attractive and affordable for international students. The article sites the fact that the GMAC has seen a 21% increase in international students registering for the GMAT test, with some MBA programs seeing the international applicant pool increasing by as much as 50% this year.
July 11th, 2008
If you haven’t heard by now, the Graduate Management Admissions Council (GMAC) – the body that administers the GMAT – is planning to revoke the GMAT scores of test-takers it feels cheated on the test or otherwise violated the rules. The cheaters, who were users of the ScoreTop VIP service, are alleged to have actively traded and distributed test questions still in use on the test (so called ‘live’ questions). ScoreTop users who have their scores revoked will be barred from attending business school. Those who have already graduated could lose their degrees.
The ScoreTop scandal raises a number of questions for GMAT test-takers, even if you haven’t previously thought about cheating. Below, the answers to a few:
What did ScoreTop users do wrong, exactly?
It seems pretty obvious that people who cheat on the GMAT should have their scores revoked. It could be difficult to say who those people were, because what constitutes cheating in this case is open to some interpretation. More troublingly, many ScoreTop users probably didn’t intend to cheat (or know they were cheating). The ‘live’ questions were presented as original questions written by ScoreTop. The ScoreTop VIP section included legitimate content in addition to ‘live’ content. It could have been hard to distinguish the good from the bad.
Potentially, any user of the ‘live’ questions is at risk. GMAC’s rules for GMAT test takers, now posted on ScoreTop’s website, state clearly: You are responsible for making sure your preparation materials don’t violate our intellectual property rights (emphasis theirs). The good news is that GMAC has said that it will revoke the scores of only those users who ‘knowingly’ cheated. GMAC’s main targets are users who posted ‘live’ questions on the site or elsewhere. Others, who commented on questions being ‘live’ (or referred to them as ‘Jungle Juice,’ in the site’s lingo) also have cause to be concerned. Casual users of the site, including all those who were unaware of the ‘live’ questions, should have nothing to worry about.
Is it wrong to use ‘live’ questions to study?
No, seriously. The stakes are high. The ‘live’ questions are out there. Other test-takers are using them. Should you
Eventually, every business school student is presented with a question very much like this one in the mandatory ethics class. The class will weigh the pros – little discernable harm to others, low probability of getting caught, greater likelihood of you becoming rich and donating millions to charity – against the cons – poorly prepared B-school students, a real (if discreet) harm to society, and the fact that it’s just plain wrong.
Save the argument for B-school. The answer on this one is: don’t cheat. It is wrong, but if you needed another reason, the truth is, cheaters don’t get much of a leg up. There are thousands of ‘live’ questions in use by GMAC at any time, and a cheater could realistically find and memorize only a handful. Most of the questions will be new to you, and even memorizing just tough questions won’t help you much (see below). If that isn’t enough to sway you, think about business school as the first step in a new, successful, and most likely challenging career. You want to get off on the right foot. You don’t want to run the risk of getting caught and seeing it disappear. And you do want to sleep soundly now - there will be plenty of ethical dilemmas down the road.
How will this effect test scores?
A few bloggers and readers have posited the interesting theory that, by virtue of cheating, the Scoretop VIP test-takers impacted others’ scores dramatically. With a few cheaters scoring highly and answering difficult questions missed by other, non-cheating test-takers, it’s suggested that the average score would be increased and normally high-value questions diminished in importance.
It’s an interesting theory. The GMAT is scored to maintain a bell curve distribution, with roughly two-thirds of testers scoring between 400 and 600. Scoring is based upon a test-taker’s overall performance (both number of questions answered correctly and the difficulty of those questions) and adjusted to maintain the target distribution. Cheaters who repeatedly answered questions correctly, especially high-value ones, and achieved high total scores could wreak havoc on GMAT scoring.
It seems unlikely to me, though. This is mainly because of the small pool of potential cheaters, the large pool of potential questions, and the adaptive nature of the test. With only 6,000 or so Scoretop VIP members (and likely no more than a small fraction actively cheating) out of a test pool of over 200,000, the cheaters’ impact is necessarily limited. Perhaps more important is the likelihood that even active cheaters would see only a handful of familiar questions, as discussed above. Putting aside the relative values of the different questions, the large number of questions not previously seen would carry much more weight in the cheaters’ final scores. Even the value of cheating on high-value questions would be limited; with an adaptive test like the GMAT the only reward for answering tough questions correctly is…more tough questions. On those occasions when a high-value question was answered correctly by a cheater, the next question would be similarly difficult (or even harder) and likely previously unseen. Incorrect answers would, over time, correct for the cheating. The total impact on non-cheaters scores would be very slight.
This isn’t the first cheating scandal to hit the GMAT, and it won’t be the last. The key to staying the clear remains the same; you should actively try to use only legitimate test prep services and tools, like Integrated Learning and the materials published by the GMAC, that we have always recommended - the Official Guide for GMAT Review, etc.
By the way, be sure to check out the “IL700: Weekly GMAT Challenge” where we offer a new GMAT practice problem each week. (We make every effort to maintain the look, feel, and complexity of the real exam with our challenge questions, while respecting all copyright laws and the policies of GMAC.)
July 9th, 2008
Yesterday, we posted a 700+ level GMAT question. Below is the answer and explanation. How’d you do?
Answer: C
Among all possible scenarios there are two that suit us:
1. A blue marble is put into the second basket and then a blue marble is extracted from the second basket;
2. A red marble is put into the second basket and then a blue marble is extracted from the second basket.
The probability of the first scenario: probability that a blue marble is taken from the first basket × probability that a blue marble is then extracted from the second basket = 4/9 × 1/2 = 4/18.
The probability of the second scenario: probability that a red marble is taken from the first basket × probability that a blue marble is then extracted from the second basket = 5/9 × 3/8 = 15/72.
The probability of EITHER first OR second scenario: 4/18 + 15/72 = 31/72.
The important thing is to understand that the probability of drawing a blue marble from the second basket depends on what marble was put there. For example, in the first scenario the probability of drawing a blue marble from the second basket is 1/2 because after one blue marble was added to the second basket, the basket contains equal number of marbles of each color.
July 9th, 2008
Every Tuesday we post a 700+ level GMAT question here on our blog, and post the answer and explanation the following day. Do you have what it takes?
The first jar contains 4 blue and 5 red marbles; the second basket contains 3 blue and 4 red marbles. One marble is randomly extracted from the first basket and put into the second. After that, a marble is extracted from the second basket. What is the probability that this marble is blue?
A. 1/3
B. 15/36
C. 31/72
D. 4/9
E. 11/18
July 8th, 2008
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