Okay, let's take this baby down. We are going to focus on the strategies behind this question that will help you answer this and many other GMAT problems. As with all Critical Reasoning questions, the first thing we need to do is a little research in the question stem. It asks us for something that would be required for the collection program to achieve its aim. Such phraseology tells us this is a “
Plan/Strategy” question, a variation on the traditional “
Strengthen” question type. This defines our strategy. With
Plan/Strategy questions, we aren’t necessarily looking for a conclusion to strengthen, but we are looking for goals. Often, the logical gap we are looking for is between the
elements of the plan and what the plan actually wants to
accomplish.
According to the stimulus, the goal is to “
reduce the amount of residual ash this year to half of last year’s total.” The plan is to separate recycling so that there are half the number of truckloads to be incinerated. Does half of the truckloads necessarily lead to half the ash? Not necessarily. Therein lies the logical gap. We need to show that the reduction of truckloads will lead to the commensurate reduction in ash. If not, the plan’s goals won’t be met.
The correct answer to this question is “
D”. However, we are going to skip “D” for a little bit to look at the wrong answers. For those of you studying for the GMAT, it is just as important to know why an answer choice is WRONG as it is to know why an answer choice is correct. Let’s watch what the GMAT does here to test your critical-thinking skills.
Quote:
(A) This year, no materials that city services could separate for recycling will be incinerated.
Answer choice “A” doesn’t address the logical gap. Pay attention to what the question is asking: we are looking for a fact "
required" by the argument to function. That is a pretty high bar. Is it
necessary that "
no materials" be incinerated if they could be recycled? No. The city could incinerate recyclable materials and still keep the truckload limit down to half of the total. While "A" adds the fact that the separated materials won’t be incinerated, it still tells us nothing about the amount of ash generated per truckload. "A" isn't required by the argument, and it doesn't tell us why half the truckloads leads to half the ash. If you picked answer choice "A", your brain inserted a lot of unjustifiable assumptions into the argument (such as recyclable materials supposedly generate the same amount of ash as non-recyclable materials.) But we don't know this. What if the recyclable materials take up large amounts of space in a truckload, but leave little ash? Answer choice “A” is not it.
Quote:
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
Answer choice “B” is an example of a beautiful trap by the GMAT I call a “
Distracting Detour.” Distracting Detours happen when the GMAT intentionally swaps out the initial goals or conclusion in a question for a different (possibly compelling) set of goals, tricking you into thinking that these alternate goals matter. However, the change doesn’t answer the question, plug the logical hole, or meet the goal. In the case of this question, the goal is to reduce ash, not reduce cost. Thus, cost is irrelevant. Answer choice “B” falls by the wayside.
Quote:
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
Answer choice “C” also doesn’t focus on the logical gap. The stimulus states that the program will remove “
recycling ENOUGH” to reduce the number of truckloads. Even if answer choice “C” were false, it would still be possible to say that we removed “
ENOUGH” recycling for the logic to work. This is especially true since we don’t know relative amounts of recycling from last year to this year to even know if it would
matter that the amount of recycling is increasing. Maybe it doesn’t matter. Answer choice “C” is out.
Quote:
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.
Answer choice “E” is very similar in nature to answer choice “C”. The plan is to remove “
recycling ENOUGH” recycling that the number of truckloads to be incinerated is half of last year’s number. Thus, even if answer choice “E” were false, it would still be possible to remove “
recycling ENOUGH” recycling. It could still be possible to have the total amount of refuse go up and still remove “
recycling ENOUGH” recycling. We don’t
need answer choice “E” for the plan to still function. Get rid of “E”.
Quote:
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
However, answer choice “D” is critical and focuses on the necessary logical gap. Remember, our gap is: “
Does half of the truckloads necessarily lead to half the ash?” Answer choice “D” talks about the ash per truckload. If each truckload generated more ash, then we wouldn’t see a commensurate reduction in ash. By saying that each truckload doesn’t generate more ash than previous years, if we can reduce the amount of truckloads by half, we are reducing the amount of ash by at least one half. Answer choice “D” is it.
Now, let’s look back at this problem from the perspective of strategy. This problem can teach us several patterns seen throughout the GMAT. First, when a question asks you for additional information that is "required" for an argument to work, focus EXACTLY on what the problem is asking. Many people miss Critical Reasoning questions because they rush too quickly through the interpretation of the question and miss crucial leverage words. Remember that "
required" information has a pretty high standard: you must look for information that is
crucial for an argument to even function, not just for information that makes the argument sound better. Focusing on the exact logical gap keeps us from falling for distracting traps and detours. And that is how you think like the GMAT.