Q20 - Council member: The profits of downtown

[Laura Damone]

What does the Question Stem tell us?
Must Be True flavor of the Inference family. Diagram if conditional. Look at forced overlap if there are a bunch of quantifiers.

Break down the Stimulus:
"if" "guarantee" and "unless" are all conditional logic indicator words, so diagramming should be our modus operandi here.

More Consumers --> Profits Up ; Cost of Living Down --> More Consumers ; Profits Up --> Traffic Down

Any prephrase?
We can link these statement up in a big chain:

Cost of Living Down --> More Consumers --> Profits Up --> Traffic Down.

Any piece of this chain, or the entire thing, or the contrapositive of any piece of the chain or the entire thing, could be the correct answer.

Correct answer:
C

Answer choice analysis:
A) This illegally reverses our chain and is therefore a standard trap answer.

B) Correct! This is a piece of our chain. Don't be deterred by the fact that it doesn't address the chain in its entirety. A common way the test writers will try to throw you off the scent of the correct answer in MBT questions is to make the correct answer accurate but incomplete. Don't be fooled! If it has to be true, it's correct, regardless of whether there are other things that have to be true as well.

C) Another illegal reversal, this time of only part of our chain.

D) Yet another illegal reversal, this time of only part of our chain.

E) Again, another illegal reversal, this time of only part of our chain.

Takeaway/Pattern: On conditional Must Be True questions, diagram and combine statements. Infer what must be true and look for an answer choice that reflects that, in whole or in part. Expect incorrect answers to illegally reverse and negate the prephrase.

#officialexplanation

[jennifer]

Does to word "guarantee" indicate a sufficent or a necessary? Thank you.

[ManhattanPrepLSAT1]

Good question. The word "guarantee" implies a conditional relationship, but it's better to not think of it the same way as "if" or "unless". Instead think of the term that provides the guarantee as the sufficient condition.

Take the statement: studying hard guarantees a good score on your final exam.

SH ---> GS

SH = study hard, GS = good score

Other words like this on the sufficiency side would be: enables, allows, and ensures. And on the necessary side: requirement, precondition, and precept. All of these words refer their respective terms, but don't necessarily introduce them.

Hope that helps!

[zainrizvi]

(A), (C), (D) can all be eliminated quickly as they make a necessary condition (downtown traffic congestion decreases) into a sufficient condition.

(E) is classic mistaken reversal.

(B) is the right answer.

[ManhattanPrepLSAT1]

nice work zainrizvi!

[js_martin01]

Might this one be solved properly by formal logic? Interested in seeing someone else's formal approach to this question.

[timmydoeslsat]

I would write down some things on this one.

This is what I have:

Decrease COL DT ---> More consumers live DT ---> Profits increase DT Biz ---> DT traffic congest decrease

As others have said, (B) must be true.

[degray]

What really throws me on this one is the line that says "However, the profits of downtown businesses will not increase unless downtown traffic congestion decreases."

What about a scenario where the cost of living in downtown decreases but traffic congestion doesn't? The profits of downtown businesses would not increase. This seems to be a possible situation in which (B) doesn't hold true. The direction are to chose the option that "must be true." It seems to me that (B) doesn't meet that criteria.

[sumukh09]

What really throws me on this one is the line that says "However, the profits of downtown businesses will not increase unless downtown traffic congestion decreases."

You'd diagram that line:

Profits will Increase ---> Traffic Congestion Decreases

We know from earlier statements that

Decrease in the cost of living ---> More consumers living in D/T area ---> Profits will increase

So we can combine that with the last statement and just add Traffic Congestion Decreases

ie) Decrease in the cost of living ---> More consumers living in D/T area ---> Profits will increase ---> Traffic Congestion will Decrease

What about a scenario where the cost of living in downtown decreases but traffic congestion doesn't?

This can't occur given the above conditional relationship. A decrease in the cost of living will guarantee that traffic congestion decreases.

[sumukh09]

What really throws me on this one is the line that says "However, the profits of downtown businesses will not increase unless downtown traffic congestion decreases."

You'd diagram that line:

Profits will Increase ---> Traffic Congestion Decreases

We know from earlier statements that

Decrease in the cost of living ---> More consumers living in D/T area ---> Profits will increase

So we can combine that with the last statement and just add Traffic Congestion Decreases

ie) Decrease in the cost of living ---> More consumers living in D/T area ---> Profits will increase ---> Traffic Congestion will Decrease

What about a scenario where the cost of living in downtown decreases but traffic congestion doesn't?

This can't occur given the above conditional relationship. A decrease in the cost of living will guarantee that traffic congestion decreases.

[aescano209]

Hey MLSAT,

I got this answer correct by eliminating all the wrong choices, but I had a question about the stimulus. It seems to me that the first portion of this stimulus provides us with causal arguments. (i.e. Cost of living decreases will cause Increased amount of people living downtown which will cause profits of businesses to increase). But the portion of the last statement with however seems like a statement that necessitates congestion to decrease in order for profits of downtown business to increase. I can see how this links up to the causal argument made prior to the 'however', but my question is doesn't this last statement say that in order for all of these causal factors to occur we must have a decrease in traffic congestion.? To my understanding the 'unless' necessitates the statement after it (lower congestion) which we would also change the first portion which is profits of businesses will not increase to 'it will increase'.

I can see how answer choice B works, but wouldn't we have to know that traffic congestion has gone down in order to conclude B since after all it is a necessary condition that needs to occur for the causal argument to be valid? I don't know if this makes sense, but I just wanted to clarify this if possible.

[NatalieC941]

Hello,

As I was short for time, I identified "traffic congestion" as a new term in the conclusion that should be in the answer choice. I was then stumped because it put "traffic congestion" in sufficient condition spot, and I didn't know how to proceed.

My question is - how do you know whether or not a "new term" mentioned in the conclusion MUST be included in the answer choice or not?

Thanks,

[ohthatpatrick]

This is an Inference question.

Inference questions are based on "statements/information", not based on "arguments/reasoning". Only the latter has a conclusion and evidence.

So there's no such thing as finding the Conclusion when you do Inference,
thus no such thing as "new term in the Conclusion".

For Inference, you're just seeing if you can combine any of the provided facts in order to derive one of the answer choices.

(as far as your question goes, though, the only time where a new term in the Conclusion MUST be in the correct answer is Sufficient Assumption)

[LukeM22]

Hey MLSAT,

I got this answer correct by eliminating all the wrong choices, but I had a question about the stimulus. It seems to me that the first portion of this stimulus provides us with causal arguments. (i.e. Cost of living decreases will cause Increased amount of people living downtown which will cause profits of businesses to increase). But the portion of the last statement with however seems like a statement that necessitates congestion to decrease in order for profits of downtown business to increase. I can see how this links up to the causal argument made prior to the 'however', but my question is doesn't this last statement say that in order for all of these causal factors to occur we must have a decrease in traffic congestion.? To my understanding the 'unless' necessitates the statement after it (lower congestion) which we would also change the first portion which is profits of businesses will not increase to 'it will increase'.

I can see how answer choice B works, but wouldn't we have to know that traffic congestion has gone down in order to conclude B since after all it is a necessary condition that needs to occur for the causal argument to be valid? I don't know if this makes sense, but I just wanted to clarify this if possible.

I just wanted to bump this as I had the exact same thought process as this guy and this taps into some thoughts I've been having about necessary conditions but haven't been able to articulate until now:

It seems that there are two ways in which we can view the last sentence "however, the profits of downtown will not increase unless downtown traffic congestion decreases":

1) Downtown congestion decreasing is an INEVITABLE OUTCOME of increased downtown profits (it 'necessarily' happens upon the occurrence of the downtown profits)

2) Downtown congestion is a NECESSARY PREREQUISITE to increased downtown profits (it is necessary to occur prior to downtown profits being realized)

In both interpretations the congestion MUST ACCOMPANY the profits but, in 1) it's made out to be something that occurs after the downtown profits, while, in 2), it's something that must be satisfied PRIOR to the event occurring, which is going to cause someone like the above poster as well as me scrambling to find a scenario where this condition is satisfied. Answer B being correct means using interpretation 1... but, at the same time, I think we can all agree that when we think of "necessary condition" we think of something that must be satisfied prior to whatever it's necessary for. But based on this interpretation, B is not a satisfactory answer, because we don't know whether the necessary condition was met. If we know someone has to be 16 in order to drive, any answer that doesn't specify whether someone is 16 doesn't give us enough information to know that that person MUST be able to drive.

The problem is that the word "necessary" is ambiguous: if A necessarily occurs prior to B, then we need to check off A before we can check off B; if A necessarily accompanies B, we don't need to check off A to know B is happening, we just know that, with B, A comes included. It's not immediately clear which type of "necessary" should have been used in this situation.

Is there a rule or at least best practice re: which of the two interpretations is better to use and when?

Thank you,

[ohthatpatrick]

Wow, these are great questions and I'll try to respond to their actual concern, but the headline for me was just:

"Why are these students thinking so hard?
It's an Inference question testing conditional logic (the most common type).
There are obvious conditional trigger words ("if", "guarantee", "unless").
We should just diagram these and see if they chain.
Then we just judge whether each answer choice is giving us a legal inference from that chain."

There is not really going to ever be a need for the distinction you're worried about between interpreting the last sentence as a guarantee or a prerequisite.

Here's the main reason you're getting confused, I think.

Saying that X is REQUIRED for Y definitely implies a chronological order. (X before Y)
but
Saying that X is GUARANTEED by Y does not imply a chronological order.

Having a driver's license is REQ'D for being a legal driver.
and
being a legal driver GUARANTEES to me that you have a driver's license.

In both cases, the license came first.

I think you got yourself thinking that when one idea GUARANTEES another, we're speaking in causal terms where the first idea ALWAYS CAUSES the second. But think of it as also accommodating LOGICAL guarantees.

To get (B) right, we don't need to consider the last sentence. The last sentence does not say, "But none of that was true, unless ...."

"If cost of living decreases, number of consumers living there will increase."
and we have a rule that says
"if number of consumers living there increases, profits will increase"
so we can derive (B), that
"if cost of living decreases, then profits increase."

If the cost of living has decreased, then we can also infer that traffic congestion has decreased. We don't need to be told that. The rules we were given say that:

if # living incr -> cost of liv decr --> profits incr --> traffic congestion decr.

So as soon as you tell me "cost of living decreases, I automatically get 'profits increase' and 'traffic decreased'.

There's no inherent timeline needed to process any of these. Just observe that we have a rule that says, "when THIS is true, THAT is true".

If you need to understand this problem chronologically, then you have to focus on the shift between future tense verbs and present tense verbs.

If cost of living DECREASES, more consumers WILL LIVE
If more consumers LIVE there, profits WILL INCREASE

The last sentence attaches the future verb to profits, making it seem like traffic congestion would be interpreted as the the first event.

So we can write it as,
If traffic congestion DOES NOT decrease, profits will not increase
and then its contrapositive becomes
If profits have increased, then we know that traffic congestion did decrease (previously)

You two were thinking of the last sentence as saying, "Until you check the box about traffic congestion, you don't know whether the first two ideas are true."

Instead, the last sentence is just a rule that says, "Oh, profits increased? Well, then HERE'S something for sure you know that happened prior to that."