LSAT Explanation PT 20, S4, Q19: Nearly all mail that is correctly

LSAT Question Stem

If the statements above are true, which one of the following must be true? 

Logical Reasoning Question Type

This is a Must Be True question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

First, let's analyze the passage. It states that nearly all correctly addressed mail arrives within two business days of being sent, and the only time it takes longer is when it is damaged in transit. However, most mail arrives three business days or more after being sent. To simplify this, let's use an example with fruits. Imagine that nearly all ripe fruits (correctly addressed mail) are sold within two days, but if they're damaged (damaged in transit), they might take longer to sell. However, most fruits (mail) are sold after three days or more.

Now, let's identify the question type and what it's asking us to do. This is a Must Be True (MBT) question, which means we need to find the answer choice that must be true based on the information provided in the passage.

Let's evaluate each answer choice:

a) A large proportion of the mail that is correctly addressed is damaged in transit.

- This answer choice is not necessarily true. We know that correctly addressed mail only takes longer than two days when it is damaged, but we don't know how often this happens. It could be a small proportion or a large proportion.

b) No incorrectly addressed mail arrives within two business days of being sent.

- We don't have enough information to conclude that no incorrectly addressed mail arrives within two days. It's possible that some incorrectly addressed mail could still arrive within that time frame.

c) Most mail that arrives within two business days of being sent is correctly addressed.

- This answer choice seems tempting, but it's not necessarily true. We know that nearly all correctly addressed mail arrives within two days, but we don't know the proportion of all mail that arrives within two days. For example, if there were 100 pieces of mail and 80 arrived within two days, but only 40 of those were correctly addressed, this statement would be false.

d) A large proportion of mail is incorrectly addressed.

- This answer choice must be true. Since most mail arrives three business days or more after being sent, and nearly all correctly addressed mail arrives within two days, a large proportion of mail must be incorrectly addressed to account for the majority of mail taking longer to arrive.

e) More mail arrives within two business days of being sent than arrives between two and three business days after being sent.

- We don't have enough information to determine the specific number of days mail takes to arrive, so we cannot conclude this must be true.

Based on our analysis, the correct answer is (D).