Q20 - If the economy is weak,

[sunhwa2881]

Can you please go over this question? Thank you~

[ManhattanPrepLSAT1]

Happy to help.

We know the following:

1. If the economy is weak, then prices remain constant, although unemployment rises.
2. Unemployment rises only if investment decreases.
3. Investment is not decreasing.

We can infer that unemployment is not rising and as such that the economy is not weak. It must be false that unemployment is rising or that economy is weak.

(A) must be false. We know from the stimulus that investment is not decreasing, and we can infer that economy is not weak. So there is noway that either one or the other of the two phenomena are occurring.
(B) could be true. We don't actually know whether those two phenomena are conditionally related.
(C) must be true and can be inferred from the first two premises.
(D) could be true since it could be true that prices are remaining constant.
(E) must be true, since we know that the economy is not weak.

Does that help clear this one up?

[peg_city]

I got this one wrong

The "although unemployment rises" part confused me

EW-->prc
EW-->ur(?)
ur-->ID
_______
ID~

ID~ --> ur~
UR~--> EW~

Is this right?

[ManhattanPrepLSAT1]

You got it. All of your statements and inferences from them are correct.

The "although" functions like an and. Other words that do that are: "yet", "even though", "while", and "but".

Great work!

[jasonxu89]

Still a little bit confused about the inferences here.

So "If A then B although C" can be expressed as

A-->B
A-->C

Are those correct?

In another

You got it. All of your statements and inferences from them are correct.

The "although" functions like an and. Other words that do that are: "yet", "even though", "while", and "but".

Great work!

[ManhattanPrepLSAT1]

So "If A then B although C" can be expressed as

A-->B
A-->C

Are those correct?

We have to be very careful with the word "although." I think I should have emphasized that above. In this instance and many others, it functions like the word "and." So yes, in this case, "if A, then B although C" can be expressed as

A --> B + C

or separating them into individual claims

A ---> B
A ---> C

Sometimes the word "although" is more reflective of a concession in an argument. In such a case, it still functions similar to the word "and" but canotes a meaning that implies that some would think it runs counter to a claim the author asserts. For an example of this check out PT26, S2, Q6 - The largest volcano.

Does that make sense?

[manoridesilva]

Hello. If anyone is still looking at this question, I am still a bit confused about answers D and E. I can see why A was a good choice, but I struggled to find good reasons to eliminate D and E.

My confusion was that we are told investment was not decreasing, hence the economy cannot be weak. I saw the full chain as this:

ew > pc + ur > id

(economy weak > prices constant + unemployment rising > investment decreasing)

Contra positives:

-id > -ur > -ew
-pc > -ew

Is D wrong because we cannot infer anything going backwards against the chain unless we use contra positives? Ie, we could infer that prices not constant = economy not weak. But we can't infer anything about the economy based on prices being constant because that is going backwards against the chain without using contra positives?

Similarly, is E wrong because we can only infer contra positives? Ie we could infer that if unemployment is not rising then the economy is not weak? But we can't infer anything about the economy based on unemployment rising because, again, it would be going backwards against the chain without using contra positives?

[irene122]

I remember "either A or B" could be diagrammed in conditional reasoning formula as follows:

not A--> B (contrapositive: not B--> A)

if why we don't have to diagram answer choices with "either...or..." as above before answering the questions?
If we diagram it, then the stimulus needs to confirm the formula; yet according to this question, we only need to confirm elements in the answer choice match the stimulus.

I am confused in what conditions we should diagram "either...or..." and in what conditions we don't have to?

Any thought would be appreciated!

[ManhattanPrepLSAT1]

Is D wrong because we cannot infer anything going backwards against the chain unless we use contra positives? Ie, we could infer that prices not constant = economy not weak. But we can't infer anything about the economy based on prices being constant because that is going backwards against the chain without using contra positives?

Answer choice (D) is wrong because it presents two ideas and while it's not possible that the "economy is weak," it is possible that prices are remaining constant.

Similarly, is E wrong because we can only infer contra positives? Ie we could infer that if unemployment is not rising then the economy is not weak? But we can't infer anything about the economy based on unemployment rising because, again, it would be going backwards against the chain without using contra positives?

Based on your question, I think you might be forgetting to include the information in the last sentence of the stimulus - that investment is not decreasing. That allows you to infer that unemployment is not rising and that the economy is not weak. So of the two options presented in answer choice (E), one of them must be true.

I am confused in what conditions we should diagram "either...or..." and in what conditions we don't have to?

It's not about needing to diagram "either/or" in either way. But I think that typically, if the "either/or" takes place within a conditional statement such as, "if G is tested, then either F or H must also be tested" - put this into a conditional as:

G ---> F or H

If you see a blanket, "either F or H must be selected" - then you could put that into the relationship as you suggested:

~F ---> H

So just keep looking for those other language cues that imply conditionality. And please let me know if you have further questions here!

[irene122]

If I understand correctly, "either...or..." should be diagrammed only when they are obviously in conditional reasoning; otherwise I just treat it as "picking one or both between two options" right?

[ManhattanPrepLSAT1]

If you decide that diagramming will help you see the connections between the statements, and you see an "either/or" involved in a obvious conditional statement place the "or" in between the terms on whichever side of the conditional relationship is appropriate.

If A occurs, then either B or C must also occur.

A ---> B or C


But if you're trying notate a statement that doesn't have an obvious "if...then" relationship but expresses something like:

Either A or else B must occur.

~A ---> B

There are times when I would notate "either A or else B must occur," using a conditional ~A ---> B and other times when I would simply set up, "A or B." I guess it just depends on the other statements that need to be connected to the "either/or" statement.

Hope that helps!

[irene122]

Thanks a lot!

[a3friedm]

EW → PRC & UR
UR → ID
~ID
_______
~EW

Question Stem: Must Be False

(A) ~EW → ID
~ID → EW

Must Be False

(B) UR → PRC

Could be true

(C) EW → ID

Must be true through the transitive property of
EW → PRC & (UR → ID)

(D) ~EW → PRC
~PRC → EW

could be true

(E) ~UR → ~EW
EW → ~UR

Must be True

[alamobile]

Hello,

I'm still trying to understand how answer choice (D) could be true "Either the economy is weak or prices are remaining constant."

We know that when the economy is weak, prices remain constant from the stimulus (WE-->PRC). Consequently, both events (economy being weak and prices remaining constant) can occur at the same.

Is my reasoning correct below for why answer choice (D) could be true?
-We know from the stimulus that the economy being weak cannot occur because investment is not decreasing. Consequently, a weak economy and prices remaining constant cannot occur simultaneously. (Can't have WE-->PRC)
-Since the economy is not weak, it could be true that prices are remaining constant.
-Thus, the condition of "Either the economy is weak or prices are remaining constant" is satisfied because it could be true that prices are constant and the economy is not weak.

Thanks in advance!

[joewoo198256]

Hello. If anyone is still looking at this question, I am still a bit confused about answers D and E. I can see why A was a good choice, but I struggled to find good reasons to eliminate D and E.

My confusion was that we are told investment was not decreasing, hence the economy cannot be weak. I saw the full chain as this:

ew > pc + ur > id

(economy weak > prices constant + unemployment rising > investment decreasing)

Contra positives:

-id > -ur > -ew
-pc > -ew

Is D wrong because we cannot infer anything going backwards against the chain unless we use contra positives? Ie, we could infer that prices not constant = economy not weak. But we can't infer anything about the economy based on prices being constant because that is going backwards against the chain without using contra positives?

Similarly, is E wrong because we can only infer contra positives? Ie we could infer that if unemployment is not rising then the economy is not weak? But we can't infer anything about the economy based on unemployment rising because, again, it would be going backwards against the chain without using contra positives?

I think an easy way to think about this is that: we know for sure that the I is not decreasing, which means U is not rising, which means E is not weak; Choice D gives us an either..or... relation; we already know that E is not weak, then P must be constant. Actually it could be true because when we negate the sufficient condition then the necessary condition may or may not happen.

Back to E, we already know U is not rising, the E must not be weak, which is a must be true(MBT) from the fact we are given.