GMAT Tip of the Week: U Can't C Me

GMAT Tip of the WeekWelcome back to Hip Hop Month on the Veritas Prep blog, where it just wouldn’t be right for a West Coast blogger to mention Biggie without also highlighting the contributions of Tupac Shakur. A visionary in the world of rap, Tupac not only blended the realms of true-art poetry with self-promotional glitz and glamour and became a pioneer in the crossover from dance (he started as a backup dancer with Digital Underground) to rap to film (his starring roles included Juice and Poetic Justice), he also foreshadowed the text-message abbreviation craze by spelling his name 2Pac and titling songs with U in place of “you,” C in place of “see,” etc.

Ironically, this artist who seemed so attuned to our iPhone/Blackberry text culture a dozen years before it came to pass actually penned the lyric “you gotta learn to hold your own; they get jealous when they see you with your mobile phone,” inferring that mobile phones were an item only for the truly wealthy and successful. If only Pac could see the world he left behind…

Tupac may also have been a GMAT visionary, as the idea of Data Sufficiency questions must have been in his mind when he wrote, in his first top-20 single I Get Around:

I hate to sound sleazy, but tease me. I don’t want it if it’s that easy.

Clearly, Tupac had an edge on Data Sufficiency questions. How?

On the GMAT, Data Sufficiency questions essentially have two paths to bait you toward a wrong answer: They can either make you think you have enough information when you don’t, or make you think you don’t have enough information when you really do. Tupac’s epic lyric above is a great mantra for avoiding the second trap:

You think you don’t have enough information when you really do.

The authors of the GMAT love to make you think that you need both statements, or answer choice C, when you in fact could do it with only one alone. If you think about the reward system, business schools (and corporations) should want to reward those candidates who can accomplish the most with the least number of resources, so it’s only natural that these questions will often be written with that in mind. Human nature dictates that we’ll feel much more comfortable with increasing amounts of information, so we have a tendency to lean toward answer choice C, which gives us all available information, and maybe steer clear of statements 1 or 2 alone, as they may appear to have some risk inherent in them.

How can we avoid this natural tendency? Channel Tupac and his line:

I don’t want it if it’s that easy.

If answer choice C seems too easy — if, at a quick glance, you know that you can solve the problem quite easily given both pieces of information — there’s a good chance that “you don’t want it,” because the test is likely to reward you for finding a way to accomplish the task with only one piece of information, not needing both. Remember, answer choice C says that both statements together but neither alone is sufficient, so if it’s possible to solve the problem with only one statement, C is incorrect. Therefore, if C looks too easy, you should return to each statement alone, and try to see which one (if not each of them) can solve the problem on its own.

One important clue: Because by this point you’ve already seen both pieces of information, a helpful method to using one statement on its own is to see if you can use it to derive the other.

Consider the question:

A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.

Here, answer choice C seems to be a fairly easy choice -– the first statement tells us that the number of full-size cars plus the number of compacts equals 7 (or, F + C = 7), and the second tells us that the total value is $66,000, or that 10,000*F + 9,000*C = 66,000. Having both equations, we know that, with two equations and two variables, we’ll be able to solve for the number of compact cars. If we assess the information in statement 2 –- that the cars cost $66,000 total –- let’s see if it’s even possible that the agency could have bought anything other than 7 cars. If not, then statement 1 is unnecessary.

If we try to purchase 8 cars, it stands to reason that if 8 of the cheapest cars cost more than $66,000, it’s not possible to purchase 8, since they would cost 8 * 9,000, or a total of $72,000. Because 8 of even the cheapest cars — substituting any of the cheaper cars with a more expensive one would only increase the total value above $72,000 — costs too much for us to reach the $66,000 total price paid, then it’s not possible to purchase 8 cars (or more). Similarly, if we test the price of 6 of the full-size cars, we will likely be able to eliminate that possibility. 6*10,000 is $60,000, which is not enough for us to reach the $66,000 total price. If we were to substitute a cheaper car for any of the more expensive cars in our set of 6, it would only decrease that total to below $60,000, so we can prove that the agency cannot purchase 6 cars for $66,000.

Because, based on the information in statement 2, the only number of cars that could be purchased is 7, the information in statement 1 doesn’t need to be stated explicitly — we already know that from our interpretation of statement 2. Therefore, the correct answer is B.

As Tupac has taught us, there’s value in the struggle, and we shouldn’t readily accept any answer that’s too easy. Don’t let the GMAT trap you with a too-easy answer choice C. As Tupac also famously said, you can’t C me.

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2 Responses

  1. dividing the 66000 by the 9000 gives 7.3 cars…shouldn't the division give a clear cut number of cars? don't I need a ratio? as well, I find the info in the stimulus to contradict the info in the stem: if the showroom have a fleet of 2 different kinds of cars, why would the stem mention it only has 7 cars of one type?my first impression after solving each of the two statements alone has lead me to choice E: I need a ratio to give the exact number of cars…

  2. Brian says:

    Good questions, Angie. A couple of clarifications:

    1) The question does not say that the agency has 7 cars “of one type”; it merely says, in statement one, that it has 7 cars “total” – it could be 7 of one type, or 6 of one and 1 of another, etc.
    2) Because of that, simply dividing the $66,000 by the $9,000 price of one type of car won’t give you the answer, as you have to account for the possibility that the agency owns, say, four $9,000 cars (for a subtotal of $36,000) and three $10,000 cars (for a subtotal of $30,000) to equal the total of $66,000.Actually, because that initial division calculation gives you a noninteger, you can be certain that the agency does not solely own $9,000 cars, as you cannot have a partial car – the number of cars must be an integer.
    3) Ratios can certainly be helpful tools on many questions, but on this one I think you may be grasping at straws to try to create one. Data Sufficiency questions are clever in that they reward your flexibility in solving problems; maybe you can't set up a ratio, but you can use other information to solve the problem. In this case, the fact that the number of cars must be an integer is a key piece of information. If the question were about pounds of flour and sugar in a bakery, for example, you could have the 7.3 pounds that you mentioned above. For cars, that won’t work. So, on this question, there may only be (and, ultimately, there only is) one combination of $9,000x + $10,000y that will add to $66,000 with both x and y as integers.

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