I'm a bit confused as to what exactly you are asking, so I'll go through an overview of missing premises for you. If you need any further clarification, please don't hesitate to let us know!
The goal of the missing premise questions is to test your ability to spot and draw valid conclusions using S&N and Quantifiers statements. There are no questions exactly like this on the LSAT, but these practice questions are testing the underlying skills you need to be successful on the Logical Reasoning section of the LSAT.
For this question, we are looking for the missing premise that allows us to conclude that B-some-C.
All the information we have to go on is that D-most-B. We must get from this premise to B-some-C.
The first step to answering these questions is to determine the contrapositive of each premise/conclusion that you are provided with.
Remember that S&N statements must be both reversed AND negated, whereas quantifiers statements (i.e. 'most' and 'some') are reversed. If it is a 'most' statement, it is reversed and changed to 'some.' If it is a 'some' statement, it is simply reversed.
Example of 'Most' Statement:
Most lawyers are athletes. This means that some athletes must be lawyers.
L-most-A A-some-L
For this question:
Premise: D-most-B Contrapositive: B-some-D
Example of 'Some' Statement:
Some kids like chocolate milk. This means that some people who like chocolate milk are kids.
K-some-LCM LCM-some-K
For this question:
Conclusion: B-some-C Contrapositive: C-some-B
So, we are looking for a way to conclude that 'B-some-C' based on the above.
Remember the two rules for making valid deductions with quantifiers:
1) Must have S&N statement 2) Must have S condition in common
Therefore, to use the transitive property to draw a valid conclusion here, we must somehow connect the premise and conclusion with a S&N statement.
Since the conclusion is B-some-C, we must use the contrapositive B-some-D to get to the conclusion. This will both allow us to use the matching quantifier and have a S condition in common that will allow us to reach the conclusion.
As the quantifier statement must precede the S&N statement, we now have:
B-some-D MISSING PREMISE B-some-C
Therefore, the missing premise is D - > C which allows us to use the transitive property:
B-some-D D - > C
Conclusion: B-some-C
If you are looking for a video explanation within the course, these concepts are discussed in the videos for Quantifiers (Section: 'Making Valid Deductions with Quantifiers') and S&N (Section: 'Transitive Property').
Hopefully this helps to clear things up a bit! Please let us know if you have any further questions.
bryanrogers21March 27, 2020
This daily drills module needs a complete overhaul. There's nothing user friendly or intuitive about them. Have spent far more time troubleshooting and looking for answers than actual time being productively "drilled".
