Does not strengthen the conclusion above EXCEPT

by **bhumrah** Fri Dec 07, 2007 3:05 pm

This question is from the MG CR practice tests.

Normally it takes a week for a cake to become moldy in a refrigerator. The cake in Alex's refrigerator is moldy. Therefore, the cake in Alex's refrigerator must be at least a week old.

Each of the following, if true, does not strengthen the conclusion above EXCEPT

A. Alex's refrigerator has not been cleaned in two years.
B. A blown fuse in Alex's building has deprived his refrigerator of electricity for the past five days.
C. The cake had just been baked when it was placed in Alex's refrigerator; it has remained there ever since.
D. A recent study demonstrated that 95% of refrigerators currently in use will keep a cake fresh for one week.
E. The cake was baked on a Tuesday.

[color=red]If we need to select a choice that "does not strengthen the conclusion, except", we select a choice that strengthen the conclusion or that is irrelevant. Right? Why can't E be the answer, as it fits "does not strengthen the conclusion, except".[/color]

Ans is C.

by **RonPurewal** Fri Dec 14, 2007 5:56 am

hi -

the way that question is worded, you're looking for the answer choice for which 'does not strengthen the conclusion' is false. that means that you're looking for an answer that does strengthen the conclusion.

choice c strengthens the conclusion, because it confirms that the cake has indeed been in the fridge for the whole time that it has been in existence. thus, it has not had the opportunity to become mouldy by other means (such as being left outside on a hot muggy summer day) before belatedly being placed in the fridge.

the other choices are either irrelevant (e is definitely irrelevant, and a is also irrelevant without lots of additional assumptions), redundant (d basically reiterates the point that cakes last a week in the fridge, which is already premise #1), or detrimental to the conclusion (d weakens the conclusion).