aurobindomahanty wrote:
At South gate Mall, mattresses are sold only at Mattress Madness. Every mattress at Mattress Madness is on sale at a 20 percent discount. So every mattress for sale at Southgate Mall is on sale at a 20 percent discount.
Which one of the following arguments is most similar in its reasoning to the argument above?
(A) The only food in Diane’s apartment is in her refrigerator. All the food she purchased within the past week is in her refrigerator. Therefore, she purchased all the food in her apartment within the past week.
(B) Diane’s refrigerator, and all the food in it, is in her apartment. Diane purchased all the food in her refrigerator within the past week. Therefore, she purchased all the food in her apartment within the past week.
(C) All the food in Diane’s apartment is in her refrigerator. Diane purchased all the food in her refrigerator within the past week. Therefore, she purchased all the food in her apartment within the past week.
(D) The only food in Diane’s apartment is in her refrigerator. Diane purchased all the food in her refrigerator within the past week. Therefore, all the food she purchased within the past week is in her apartment.
(E) The only food that Diane has purchased within the past week is in her refrigerator. All the food that she has purchased within the past week is in her apartment. Therefore, all the food in her apartment is in her refrigerator
Source : LSAT PrepTest54 Q23
(C)
Parallel Reasoning (Formal Logic)When a
Parallel Reasoning stimulus contains Formal Logic keywords, jot down the statements in abstract form before approaching the choices.
Every mattress sold in Southgate Mall is sold at Mattress Madness (“
Every X is Y”). Every mattress sold at Mattress Madness is on sale at a 20 percent discount (“
Every Y is Z”). Therefore, every mattress sold at Southgate Mall is on sale at a 20 percent discount (“
Therefore, every X is Z”). The right answer won’t mention Southgate Mall or Mattress Madness, so we need to take this abstract framework to the answer choices and find the perfect match.
(A) does not match the logic of the stimulus. All the food in Diane’s apartment is in her fridge (“All X is Y”) and all the food she purchased in the last week is in her fridge (“All Z is Y”). This doesn’t mean, though, that all the food in her apartment was purchased in the last week (“All X is Z”).
(B) is not a match. All the food in Diane’s fridge is in her apartment (“All X is Y”) and all the food in Diane’s fridge was purchased in the last week (“All X is Z”). But the conclusion that all the food in Diane’s apartment was purchased in the last week (“All Y is Z”) just doesn’t follow. What if Diane has purchased some food and stored it in the pantry? The stimulus doesn’t leave any loopholes like this. Eliminate.
(C) is the winner and has all the elements: All the food in Diane’s apartment is in her fridge (“
Every X is Y”) and all the food in her fridge was purchased in the last week (“
Every Y is Z”), so all the food in Diane’s apartment must have been purchased in the last week (“
So, every X is Z”). Same classic syllogism as the stimulus.
(D) is not a match. It starts off correctly, but its ending is backwards. All the food in Diane’s apartment is in her fridge (“All X is Y”) and all the food in Diane’s fridge was purchased in the last week (“All Y is Z”). But that doesn’t mean that all the food Diane purchased is in her fridge (“All Z is X”). Diane could have purchased some food in the last week that didn’t end up in her refrigerator.
(E) is not a match. It says that all the food Diane purchased in the last week is in her fridge (“All X is Y”) and that all the food she purchased in the last week is in her apartment (“All X is Z”). But then (E) tries to conclude that all the food in Diane’s apartment is in her fridge (“All Z is Y”). Eliminate.