Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fac...

Ravi February 19, 2019

@Adam-Estacio,

Happy to help.

From the stimulus, we know that we have two types of mail.

1) correctly addressed mail
2) incorrectly addressed mail

We know that correctly addressed mail always arrives on time unless
it's damaged.

For incorrectly address mail, we don't know anything.

We're also told that most mail arrives late. That's odd. This means
that most mail either is incorrectly addressed or it's correctly
addressed and damaged. However, we also know from the stimulus that at
most only a few of the correctly addressed mail is late. We know this
because we're told in the first sentence that "Nearly all mail that is
correctly addressed arrives at its destination within two business
days of being sent." This means that it must be the case that there is
a lot of mail that's incorrectly addressed.

The question asks, "If the statements above are true, which one of the
following must be true?"

(A) says, "A large proportion of the mail that is correctly addressed
is damaged in transit."

You were thinking that this could be true. The problem with (A) is
that it contradicts the first sentence, as we're told that nearly all
mail that's correctly addressed arrives at its destination within two
business days. If this is true, then it certainly doesn't have to be
true that a large proportion of the mail that is correctly addressed
is damaged in transit, as we know a minority of this mail is damaged.

(D) says, "A large proportion of mail is incorrectly addressed."

(D) has to be true because we know that most mail arrives late, and we
also know that most correctly addressed mail arrives at its
destination on time. This means that in order for most of ALL mail to
be late, a very large fraction of all mail has to be incorrectly
addressed.

Does this make sense? Let us know if you have any more questions!