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We're here to talk about must be false questions in the logical reasoning section.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
These guys are pretty rare, only about 1% of questions.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So on most tests, we don't see any of these.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And when we do see them, typically it would only be one per test.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We want to talk about how to spot one, how we should think about reading it and breaking it down.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
What sort of reasoning structures are likely or unlikely to show up, and what sort of trap answers we might look out for.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Here are a few examples of a must be false questions, then, which of the following must be false key words, too obvious, which cannot be true.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If the statements above are true, that tells you you're doing some sort of inference question, because they're calling the paragraph statements rather than an argument or reasoning.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And instead of asking us what must be true or what's most supported as a typical inference question would, this actually says which can't be true.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
This one feels a little bit more like logic games, where we are often asked each of the following could be true except, and we know to convert that into four of them could be true, one of them must be false.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
There's a software version of this that's sort of like the difference between must be true and most supported.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Instead of flat out saying must be false, they'll just say it's the least compatible.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
But when Elsaid uses the term incompatible or incoherent, it means contradictory.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So the least compatible means the most contradictory.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Again, this question stem is referring to the paragraph as statements, which tells us we'll be reading facts and information, not an argument.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
When we're in the inference family, we're not reading arguments.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So we're really reading facts and seeing if they have any relation to each other, particularly we look out for conditional and causal relationships.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We look for overlapping ideas.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If something's being brought up more than once, then usually we can derive something by combining the two facts we're given about a certain thing.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we are reading and we see conditional logic wording, we'll definitely start thinking about maybe diagramming some of the conditional logic.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we see comparative or causal wording, which is much less rare here, then we might enter more of that sort of mindset, seeing if there's a causal chain or trying to sort of itemize where are their similarities, where are their differences between these things being compared.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
When it comes to step three, anticipating an answer, there are two main directions that you will usually see a correct answer go on a must be false.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It'll typically either contradict a conditional statement that we were given, or it'll contradict a possible inference that we could have made.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Let's look at each of those.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So let's say that Solomon is a polite eater.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
He only double dips his shrimp when the cocktail sauce is down to its last bits.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And he often uses a wet nap after he's done.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we were being asked which of these must be false, could it be true that using a wet nap is considered impolite?
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Kind of tempting.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
I mean, we said Solomon was polite.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We said Solomon uses a wet nap.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So this feels like it's going against that.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It's saying using a wet nap impolite.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
However, it never connected politeness to using a wet nap.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Both of those things were mentioned, but it never said, if you're a polite eater, you always use a wet napkin after you're done eating something messy.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So this does not contradict anything.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
He says that he always uses a wet nap before he eats.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And we might think, well, we don't know that.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We only heard that he uses it after he's done eating.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
OK, this is wrong.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
But is it contradicting anything?
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The danger on must be false is that we confuse something that we wouldn't be able to prove with something that is provably false.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So we don't have any idea.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Maybe he uses a wet nap before he eats and after he eats and throughout, he goes through a lot of wet naps when he sits down to eat shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
All of that is compatible with the passage.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
See says that at his birthday party, he took a fresh bowl of cocktail sauce out of the fridge and dipped his shrimp in it twice.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It seems like a relatively innocuous idea.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
But wait, we were given a rule that says he only double dips if it's down to the final bits.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And this is a fresh bowl.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So this actually does contradict something we were told.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We were told a conditional, signified by the word only when.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Only and only if and only when always indicate necessary conditions.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So this is actually telling us that in order for him to double dip his shrimp, it's a requirement that the cocktail sauce is down to its last bits.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Required things go on the right.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
That's called the necessary condition, the required, the necessary thing.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The contrapositive would say, if the sauce isn't down to its last bits, he's not going to double dip his shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
But we were just given a counter example.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
When you're trying to contradict a conditional, it has nothing to do with negating or controposing.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It just means provide one counter example.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The form of a counter example is always something in which the trigger happens, but the outcome doesn't.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So in this case, he doubled dips, but it was not the case that the sauce was nearly done.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The C would be the correct answer here.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It contradicts a conditional.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
One of the ways in which they make that answer less obvious and less appealing is by putting in extra details like birthday party or his fridge.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we see a conditional in the statements, we should pay a lot of attention to it because it's very likely that a correct answer will do this, say that the trigger happens, but say that the outcome isn't happening.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The other type of correct answer on a must-be-pulse question is an answer that contradicts something that we could have inferred from the statements by pulling two or more facts together.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we look at these statements, Solomon has been trying to cut down on his shrimp eating.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
For the past two weeks, the number of shrimp he's been eating has indeed declined, although the total weight of shrimp he's eating has not.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And every day he writes another blog article about freeing himself from the tyranny of shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If it wasn't already obvious, these are not very realistic L-set paragraphs.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So if we're being asked here, which of the following must-be-pulse pause the recording and take a look at these three answers, and then unpause when you want to hear about them.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Welcome back.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Is it possible that no one, including Solomon, reads his blog?
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It is.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
All we know is that every day he writes another article.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We don't know if he reads that article.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We don't know if anybody else reads that article.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So it is possible that he is just typing these and no one is ever reading.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
A could be true.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
B says that the shrimp he was eating a month ago are heavier than the shrimp he's eating now.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Well, that actually is contradicting something we know.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
There was a comparative relationship there that the number of shrimp has gone down, but the total weight of shrimp has not gone down.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we think about the math involved, your total weight of shrimp is just how many shrimp you ate times the average weight per shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If I eat 10 shrimp and on average, they each weigh about 20 grams, and I eat 200 grams of shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
If we find out that he's eating the same total weight or at least as much, even though the number of shrimp has gone down, then the only way to balance out that math is to infer that the average weight per shrimp has gone up.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The possible inference these facts allowed us to make are that for the past two weeks, he's been eating on average heavier shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
B contradicts that idea and says that the shrimp he was eating a month ago are heavier than the shrimp he's eating now.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Now, there are slight technicalities with a month ago in the sense that our paragraph never exactly clarified what Solomon is doing a month ago, but we will take this as a 98% provably false type answer.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
C says that he only writes blog articles about shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Can we infer that?
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Heavens no.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
We know he writes blog articles about shrimp, but he might write blog articles about other things as well.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
I've heard he has a passion for wet naps.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So C could be true, could be false.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
The important thing is it doesn't contradict anything.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
In order for us to pick C, we would have to be able to tell from this paragraph that he writes blog articles about things other than shrimp.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
And we haven't heard anything like that so we have no way to contradict it.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
So B was our correct answer.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
It contradicted a mathematical inference we could pull out of that comparison.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg
Again, the two patterns for correct answers are that they will contradict a conditional statement that gave us, or it will contradict a possible inference we could have made.
Must be False
"2021-07-06 13:00:03 UTC"
_9fM5XUMpYg

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