The standard policy of the mail delivery system of Bainsbury is to hold registered mail at the post office and ask the intended recipients to drive to the post office in order to retrieve it. Last year, this policy generated long waits at the post office, due to the fact that government tax returns are all delivered on the same day by registered mail, as are many holiday cards and packages, and the post office was flooded with visitors. The post office is expecting the same amount of registered mail on the day that government tax returns are delivered this year as it received on the corresponding day of last year. In order to reduce the wait time at the post office on such days to half of what it was last year, the post office has changed its policy. This year, the post office will take half of the bags of registered mail on tax days and holidays and deliver their contents by hand to their intended recipients.
Which of the following must be true for the post office's plan to achieve its goal on days with unusually high quantities of registered mail?
The question is asking for the assumption. The assumption is the missing link: what must be true for the premises to connect to the conclusion.
Premises:
Same amount of registered mail this year.
Half the bags to be delivered this year.
Conclusion:
Wait time will be reduced by half.
Assumption:
The argument connects delivery of the bags to a reduction in wait time. What is the missing link?
The people. The bags don't wait in line; people do. The argument assumes that the number of people associated with each bag will be unchanged.
A
Delivering half of the registered mail received on holidays will cost the Bainsbury post office no more than delivering non-registered mail on days with regular mail volume.
Out of scope. The argument is not about cost.
B
This year, every piece of registered mail that is being held at the post office must be addressed to a recipient for whom no other piece of registered mail is being held at the post office.
Every piece? So if one piece of mail being held at the P.O. is addressed to a recipient who has another piece of mail being held at the P.O., the plan won't work? Too strong. This answer choice doesn't have to be true, so it's not the assumption.
C
The average number of visitors to the post office per bag of registered mail delivered this year will be no higher than the average number of visitors to the post office per bag of registered mail delivered last year.
Correct. If the average number of visitors per bag does not increase, then fewer bags at the P.O. means fewer visitors. This is the missing link: what must be true for the wait time to be reduced.
Also, this answer choice passes the negation test. The assumption is something that must be true for the argument to be valid. Thus, when the correct answer is negated, it must invalidate the conclusion of the argument. Reversed, answer choice C would say:
The average number of visitors to the post office per bag of registered mail delivered this year will be higher than the average number of visitors to the post office per bag of registered mail delivered last year.
If the average number of visitors per bag is higher, then the wait time will not be reduced, invalidating the conclusion of the argument.
D
Registered mail delivered to Bainsbury will constitute a smaller percentage of all mail delivered this year than it did last year.
Out of scope. The argument is not about registered mail versus all mail.
E
The total number bags of registered mail delivered to Bainsbury this year will be smaller than the total number of bags of registered mail delivered to Bainsbury last year.
Not the missing link. The argument states as a fact that the amount of registered mail is not changing.
The correct answer is
C.
Here's a good take-away:
The argument above is making an analogy: it is comparing this year to last year. In an analogy,
the assumption is that the two things being compared are similar. The argument above assumes that since the amount of mail is expected to be the same, all other conditions will remain the same. Other assumptions being made in the argument above:
-- that the number of post offices will not change
-- that the number of post office employees will not change
-- that the post offices will be open for the same number of hours per day
Hope this helps!
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