Traffic engineers have increased the capacity of the Krakkenbak Bridge

Question

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.

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.

siddharthfrancis · Answer

why is the answer B ?? Why is C wrong. Please explain.

GMATRockstar · Answer

This question is tagged "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?

So, I could almost think of like a more 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

(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.

akela · Answer

PowerScore Complete Question Explanation

Must Be True—SN. The correct answer choice is (B)

This conditional reasoning question appears more complex than it is due to the fact that the conditional language is all in the negated form. The question becomes much easier to work with if you take the contrapositive of the conditional statements, thus translating them from the negative into the positive. Conceptually, we can think about the conditional statements as attempting to tell us what is necessary for each sufficient condition to happen. Breaking down the language in the stimulus to the bare-bones idea in each statement will make any Sufficient-Necessary problem easier to manage.

Looking at the stimulus, we see a chain of conditional relationships. The increase in traffic flow required the city to make the investment in modeling technology. The resolution of the city’s financial predicament required the increase in traffic flow. We can note that the increase in traffic flow is the common term. We can diagram the relationship between both statements as follows:

Resolution of financial predicament ----> Increase in traffic flow ----> City to make investment

Once we can see the simple chain, we are ready to turn to the answer choices.

Answer choice (A): Information unrelated to the conditional chain above is unlikely to be correct. In a Must Be True question, we are limited to what we know for certain from the facts in the stimulus. The stimulus provides no background on how the city decided on the particular modeling software used. The stimulus lacks information to support this answer choice.

Answer choice (B): This is the correct answer choice. This is the contrapositive of the conditional chain. If the city did not make an investment, the financial predicament would not have been resolved. This is because the resolution required the increased traffic flow, which in turn, required the investment.

Answer choice (C): From the stimulus, we know that the bridge can handle increase in rush-hour traffic flow. This answer choice does not limit itself to rush-hour; it states a fact about the day as a whole. We cannot draw any inference about the number of cars that cross the bridge in an average day, just about the short rush-hour periods. While this answer choice may seem likely to be true, and in fact could be true, remember that we are looking for the answer choice that must be true.

Answer choice (D): Like in answer choice (A), we do not have information about how the city made the decision to use the modeling software, or how the ultimate decision to go forward with the change to the bridge was made. Notice here that the unsupported portion of the answer choice was at the very end of the answer choice, and students who merely scan the answer choices or who are in a rush might miss the additional unsupported information.

Answer choice (E): Similar to answer choices (A) and (D), this answer choice is incorrect due to a lack of information. We do not know why the mayor supported getting the modeling software. We just know that he did purchase it. There could have been additional uses for the software.

sssanskaar · Answer

Guys, I'll be honest. This question can be solved immediately if you are aware of the concept of the necessary-sufficient conditions. This basically means: Only because the city has invested in modeling technology, the increase in rush hour traffic flow has occurred. This basically means: Only because the increase in rush hour traffic flow has occurred, the city’s financial predicament has been resolved. Join these two sentences - Only because the city has invested in modeling technology, the city’s financial predicament has been resolved. Or in other words, Option B.

kanikaa9 · Answer

Investment in Comp Model --> Increase in Traffic --> Increase in Bride Cap --> Better Financial situation

B

repellatquas · Answer

I tried to solve it another way using conditional statements (If X, then Y). 
Given if the city had not invested in technology, then traffic flow would have not increased. 
That is, CT' -> TF'

Also, if traffic flow would not have increased, then financial predicament would not have resolved 
That is, TF' -> FP'

A very simple inference of A->B and B->C is A->C

Therefore, CT' -> FP' 
Meaning, If city had not invested in technology then financial predicament would not have been resolved. 
 B 
Hope this helps.

Traffic engineers have increased the capacity of the Krakkenbak Bridge

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GMAT Critical Reasoning (CR) Questions

Traffic engineers have increased the capacity of the Krakkenbak Bridge

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More than Quant/Verbal Abilities: Speed vs. Accuracy

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