We can be sure that at least some halogen lamps are well crafted, because halogen lamps from most major manufacturers...

Nicolette on September 16, 2014

Please explain

The answer is B. However, I do not understand how this matches the reasoning in the argument. When I diagram I do not get parallel results. I chose C, and do not see how it is incorrect.

1 Reply

Melody on September 23, 2014

Let's break down the argument:

"Any item on display at Furniture Labyrinth is well crafted."

PR: ODFL ==> WC
not WC ==> not ODFL

"halogen lamps from most major manufacturers are on display at Furniture Labyrinth."

NOTE: These are a specific type of halogen lamp--those from most major manufacturers. We do not know how many other types there are. Thus, we will write this out "some halogen lamps are on display at Furniture Labyrinth."

P: HL-some-ODFL
ODFL-some-HL

Thus, "we can be sure that at least some halogen lamps are well-crafted."

C: HL-some-WC
WC-some-HL

Remember, we can connect a "SOME" statement to a Sufficient & Necessary statement if the right-hand side variable of the "SOME" statement is the same as the sufficient condition of the Sufficient & Necessary statement. We have this scenario in the above argument, so we can combine "PR" and "P1" as follows:

HL-some-ODFL ==> WC

From this we can conclude: HL-some-WC, which is our conclusion. Our correct answer will have the same exact reasoning as the argument above.

Answer choice (B) states: "We can be positive that there are at least a few disturbing sonnets, given that Melinda has written several different kinds of sonnets; everything Melinda writes is disturbing."

Let's break the argument down.

"everything Melinda writes is disturbing."

PR: MW ==> D
not D ==> not MW

"Melinda has written several different kinds of sonnets;"

P1: MW-some-S
S-some-MW

"We can be positive that there are at least a few disturbing sonnets,"

C: S-some-D
D-some-S

Just as in the stimulus, we have a "SOME" statement whose right-hand side variable is the same as the sufficient condition of the Sufficient & Necessary statement. So, we can combine "PR" with "P1" like so: S-some-MW ==> D to conclude: S-some-MW. Thus, answer choice (B) is the correct answer because it has the exact same reasoning as the argument in the stimulus.

Answer choice (C) states: "We can be sure that Gianna will get at least some good mechanical work done to her car, because she can have her car worked on at any several shops in the city, and every shop is capable of doing good mechanical work."

"every shop is capable of doing good mechanical work."

PR: S ==> CGMW
not CGMW ==> not S

"she can have her car worked on at any of several shops in the city,"

P: S

"We can be sure that Gianna will get at least some good mechanical work done to her car,"

C: some GMW

As you can see, this does not have the same reasoning as the argument in the stimulus. In the stimulus we combine a Sufficient & Necessary statement with a "SOME" statement to properly conclude a "SOME" statement.

This argument does not have a premise that is a "SOME" statement. The sentence "she can have her car worked on at any several shops in the city," is neither a Sufficient & Necessary statement, nor is it a Quantity statement. It's merely a statement of fact that acts as one of the premises.

Hope that clears things up! Please let us know if you have any other questions.