How to Make Inferences on GMAT Critical Reasoning

Let’s look at the following CR problem:

Traffic engineers have increased the capacity of the Krakkenbak Bridge to handle rush-hour traffic flow. The resultant increase in rush-hour traffic flow would not have occurred had the city not invested in computer modeling technology last year at the request of the city’s mayor, and the city’s financial predicament would not have been resolved if the traffic flow across the bridge during rush hour had not been increased.

This question is a little bit like a “must be true,” but if we look at the wording of the Q-stem:

Which one of the following can be properly inferred from the information above?

…we can see it is more of a general “could be true” CR Inference question. Breaking down the argument:

-Bridge capacity increased
-More flow possible due to Tech from mayor
-If traffic flow hadn’t increased, then $$$ problems

Before we look at the answer choices, we need to consider what inferences can be made based on these three facts. Since we only have three facts, there really aren’t too many inferences we can make without bringing in outside info, and ideally, we want an inference that will “unite” at least two of these facts.

Prediction: $$$ problems were so bad it justified spending $$ on Tech to fix the traffic

Let’s look at the official wording of the answer choices:

Which one of the following can be properly inferred from the information above?

(A) The city’s financial predicament would not have been resolved had the city chosen a competing computer modeling software package.
(B) The city’s financial predicament would not have been resolved had the city not invested in computer modeling technology.
(C) On an average day, more traffic crosses the Krakkenbak Bridge this year as compared to last year.
(D) Traffic flow across the Krakkenbak Bridge during rush hour would not have increased had the city’s mayor not made investing in computer modeling technology the highest budgetary priority last year.
(E) The city’s mayor was a proponent of investing in computer modeling technology because of the city’s need to increase traffic flow across the Krakkenbak Bridge during rush hour.

Here’s how we can analyze each one:

(A) We don’t know anything about the various different possible Tech, so this cannot be inferred. Eliminate.
(B) It is possible that only by spending $$$ on the Tech that the $$$ problem is solved, since we had to fix the traffic issue to avoid the $$$ problems. Keep.
(C) The actual numbers of traffic on a given day don’t relate at all to the last two sentences of the argument, so we can tell this will not be correct. Eliminate.
(D) If mayor didn’t make Tech #1, flow wouldn’t have increased. This relates better than (A) and (C), so let’s hang on to it for now. Keep.
(E) Mayor wanted Tech b/c of traffic issue. This is a little like (E), but it focuses unusually on the desires on the Mayor as a person, and that’s not really the focus of the argument, which is more about financial problems and the results of investing in Tech. Eliminate.

Let’s examine the Final Two:

(B) The city’s financial predicament would not have been resolved had the city not invested in computer modeling technology.
(D) Traffic flow across the Krakkenbak Bridge during rush hour would not have increased had the city’s mayor not made investing in computer modeling technology the highest budgetary priority last year.

The phrase “highest budgetary priority” in (D) really tilts our hand to (B) here. (B) does a nice job combining the final two statements without making any kind of weird, outside the box claim. It’s the safest inference, and therefore correct.

Takeaway: Differentiate between Inferences that ask you what “MUST” be true versus what “COULD” be true. Understanding the specific wording of the question-stem will help you choose the right answer!

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