Nearly all mail that is correctly addressed arrives at its destination

Question

Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fact, correctly addressed mail takes longer than this only when it is damaged in transit. Overall, however, most mail arrives three business days or more after being sent.

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

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

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

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

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

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

Source  :  LSAT PrepTest20 Q#19

mikemcgarry · Accepted Answer

Apparently this is a practice LSAT Analytical Reasoning question, and it's an excellent question. I'm not sure whether MLSAT is the source, but it is discussed on this page: https://www.manhattanlsat.com/forums/post407.html OK, let's think in terms of categories. Category P === correctly addressed mail Category Q === incorrectly addressed mail That's the big breakdown. At the outset, we have no idea of the relative breakdown of these two, but the whole "population" of mail falls into one of these two categories. Category P has the further breakdown Category P1 = correct addressed and not damaged ---- this is " nearly all " of Category P, and this arrives " within two business days of being sent " Category P2 = correctly addressed by damaged in transit --- this is some very small fraction of Category P (whatever the opposite of " nearly all " is!), and it doesn't arrive quickly We absolutely know that mail in Category P1 arrives within two days. How fast does mail in category Q arrive? We can draw absolutely no conclusion about this. We also have no idea what proportion arrives earlier and what proportion arrives late. Given the last piece of information --- " most mail arrives three business days or more after being sent " --- from this, we absolutely know that P1 does not account for a majority of mail. If P1 is less than half of mail, we know P2 is going to account for such a small percentage that it doesn't matter, and this means Q must account for the majority of mail. This is precisely what (D) says. This is by far the best answer, the only possible right answer. Why is (A) wrong? This directly contradicts the statement that NEARLY ALL correct addressed mail arrives within two days and therefore is not damaged. Why is (C) wrong? Well, this one could be true, but it is not necessarily true --- it doesn't reach the standard of " must be true " for which the question is asking. Consider these two scenarios. Scenario #1 : P1 = 39% P2 = 1% Q = 60%, and all of it arrives late This scenario is consistent with all the statements in the argument, and this supports answer (C) Scenario #2 : P1 = 19% P2 = 1% Q = 80%, and this consists of two sub-categories Q1 = 25% --- arrive in two days days Q2 = 55% --- arrives in three or more days Now, all the statements in the argument are still true --- it's still true that the majority of mail --- 56% (P2 + Q2) arrives late --- but now if we look at the 44% that arrives on time, 25/44 comes from Q, the incorrectly addressed mail, and 19/44 comes P, the correctly addressed mail. Thus, the majority of mail that arrives on time, 25/44, comes from category Q, the incorrectly addressed mail. This is a scenario totally consistent with the argument in which (C) is false. Thus, we can construct scenarios consistent with the argument that make (C) either true or false, so it is not a candidate for a " must be true " answer. The only viable answer is (D) , the OA. Please let me know if anyone reading this has any further questions. Mike :-)

hypermeganet · Answer

I will try and do my best to answer this one again. Since this is LSAT logic it is really far more advanced than anything you'll see on the GMAT. I'm getting -0 CR on my GMAT practices and this problem is probably 10 times harder than anything I've seen in GMAT prep.

Let's break down the stimulus:

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

If mail is correctly addressed then it arrives within 2 days.
If mail does not arrive within 2 days it is not correctly addressed.

In fact, correctly addressed mail takes longer than this only when it is damaged in transit.

If correctly addressed mail does not arrive within 2 days then it is damaged.

Overall, however, most mail arrives three business days or more after being sent. If the statements above are true, which one of the following must be true?

So we know that if mail is correctly addressed it arrives within 2 days unless it is damaged. We also know that nearly ALL correctly addressed mail arrives within 2 days, meaning that most correctly addressed mail is NOT damaged.

How else can we account for the fact that mail takes longer than 2 days? It must be incorrectly addressed. D.

So, why is C wrong?

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

This is what is called a mistaken reversal.

If mail is correctly addressed then it arrives within 2 days, per above. This does NOT mean that if a letter arrives within two days it is correctly addressed! That is a key point. The stimulus says the only way mail  CAN TAKE LONGER  is for it to be damaged or incorrectly addressed. This does not mean that incorrectly addressed mail  MUST  take longer than two days. For all we know 100 letters are delivered, 99 of which are incorrectly addressed. 19 of these letters arrive within 2 days and 81 arrive after 2 days. Only one of these is correctly addressed but the majority take 3+ days.

Bunuel · Answer

OFFICIAL EXPLANATION

D

Our job here is to draw an inference from the several timing statements contained in the stimulus. Here’s the situation: nearly all mail that’s correctly addressed arrives within two business days. The only time correctly addressed mail takes more than two business days is if it is damaged in transit. Overall, however, most mail takes three days or more to get to its destination. How can we reconcile this last idea with the statement in the first two sentences? Like this: we must infer that most mail is not correctly addressed, choice (D).

Think about it this way: the correctly addressed mail is a subset of the larger group called “overall” mail. And if most mail in this larger group takes three business days or more, yet most of the correctly addressed mail arrives within two business days, then there must be another group contained in the “overall” mail group that drives the “overall” arrival number up. The only other group besides “correctly addressed mail” is “incorrectly addressed mail,” and there must be a lot of it out there if the number in the last sentence is correct.

(A) can be true, but need not be; so we can cross it off (see bullet point below).

(B) There must be a lot of incorrectly addressed mail taking three business days or more in order to drive the overall number up, but that doesn’t mean that every incorrectly addressed piece of mail arrives this late. That is, it is possible for some incorrectly addressed pieces to arrive within two business days.

(C) Most correctly addressed mail arrives within two business days. We can’t switch this around and say that most mail arriving within two business days is correctly addressed.

This choice may sound good at first; but if you look at it really hard, you’ll see this is backwards and therefore cannot be inferred. It’s possible that most mail that shows up within two business days is incorrectly addressed.

(E) is an overly precise claim that we have no way of verifying from the information in the passage.

• Continually hone your ability to interpret formal logic statements. The statement “correctly addressed mail takes longer than two business days to arrive only when it is damaged in transit” literally means “if correct address and longer than two days, then damaged.” It doesn’t mean “if damaged, then longer than two days.” Now, you may have thought that (A) cannot be true, but in fact it can: it’s possible for a large proportion of correctly addressed mail to be damaged and still to have nearly all correctly addressed mail arrive within two business days.

hypermeganet · Answer

Oooh, an LSAT question.

Most correctly addressed (CA) mail ---> 2 days or less
CA Damaged in transit ---> More than 2 days
Most mail takes more than 2 days

D is the correct answer. Mail only takes longer than 2 days if it is damaged (and CA) or if it is incorrectly addressed. Since nearly all CA mail is < 2 days, we know that most mail being delivered is incorrectly addressed.

hypermeganet · Answer

Re: C

Most of the mail arriving within 2 days could be incorrectly addressed. This confuses sufficient and necessary conditions.

If the mail is correctly addressed then most will arrive within 2 days.
 If it doesn't arrive within 2 days it was not correctly addressed.  This is the contrapositive and the key to the problem.

Since the majority of the mail didn't arrive within 2 days it is incorrectly addressed. D.

We know that the majority of mail that is correctly addressed is undamaged per the stimulus so this isn't really an issue.

Does this help?

PTK · Answer

my ans was С, but it is wrong.

D is correct- reasoning is:
 
Statements: 
- normally correctly adressed letter arrives in 2 days 
-correctly addressed mail takes longer than this only when it is damaged in transit.
- Reallity: Overall, however, most mail arrives three business days or more after being sent

Delyas may be due to:
 -if correctly adressed, delay is due to damage;
- if incorrectly adressed, delay is due to incorrect adress.

Reality is : most mail arrives three business days or more. 
Two variants are: 
-most are correcly adresesed few are damaged, thus delay - so in average 3 days. 
-most are incorrectly adressed, few/any are damaged - so avearage is 3 days.

A) A large proportion of the mail that is correctly addressed is damaged in transit.
what if mails are incorrectly adressed and damaged?  - may be false may be true.
 
B) No incorrectly addressed mail arrives within two business days of being sent. - we don't know. too strong.

C) Most mail that arrives within two business days of being sent is correctly addressed.
 - reversed statement.  
D) A large proportion of mail is incorrectly addressed.  -supported by stimuli. (yes, even if it is not logical, this is GMAT world!)

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 know since we do not have any figures here or other numerical clues.

nusmavrik · Answer

How can A be the answer?
2 cases
1) Less than 2 days - correctly addressed
2) More than 2 days - damaged or incorrectly addressed. 
Both cases are  almost mutually exclusive  - 99%. There can be 1% exception. A is worst choice that directly contradicts the premise.

Choice E - There is no data to verify E.

fluke · Answer

We know correctly addressed mails arrive within 2 days.
We know that overall arrival time of all mails is equal to or greater than 3 days.

Means what; the weight of the mails that arrived beyond 3 days IS greater than the weight of the mails that arrived within 2 days. And, what kind of mails arrive beyond 3 days. Incorrectly Addressed OR Correctly addressed but damaged in transit. Now, we need to make subtle assumption here. Correctly addressed but damaged in transit WILL not be that many because "NEARLY ALL mail that is correctly addressed arrives at its destination within two business days", i.e. there are very few- perhaps negligible- that are damaged. Also, this number will ALSO be neutralized by the number of mails that are incorrectly written but arrive within 2 days.

Seeing all this "D" seems to be the best.

A) A large proportion of the mail that is correctly addressed is damaged in transit.
This directly refutes the premise. "NEARLY ALL mail that is correctly addressed arrives at its destination within two business days"

B) No incorrectly addressed mail arrives within two business days of being sent.
Nothing of this sort is mentioned. There can be few mails that were incorrectly written but were delivered on time. We just know that if a mail arrived beyond 2 days, it was either incorrectly addressed OR damaged.

C) Most mail that arrives within two business days of being sent is correctly addressed.
Now, this seems plausible but may not be true.

It can happen like this:
100- Correctly written: Arrived within 2 days.
1000- Incorrectly Written: Arrived within 2 days.

But,
(1100+x): x is some number, Incorrectly addressed mail will have to arrive beyond 3 days.

E) More mail arrives within two business days of being sent than arrives between two and three business days after being sent.
We can't be sure of this one too.

100- Correctly written - arrived within 2 days
5-Incorrectly written OR Damaged- arrived between 2 and 3 days
>105 incorrectly written arrived beyond 3 days.

Ans: "D"

aditya8062 · Answer

i just checked and found that the proclaimed answer to this question is D

why D cannot be answer? 
reasoning:  D says : A large proportion of mail is incorrectly addressed.

we know that  "most mail arrives three business days or more after being sent"  ------->there can be a situation where in a  CORRECTLY ADDRESSED  mail is  DAMAGED  and is arriving  LATE  and that  SUCH TYPES  of mails are constituting a large proportion (say 90%) hence D is negated !!

kinjiGC · Answer

Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fact, correctly addressed mail takes longer than this only when it is damaged in transit. Overall, however, most mail arrives three business days or more after being sent.

Almost all the correctly addressed mail -> Arrives within 2 days
Correctly addressed -> If it takes longer -> the mail is damaged in transit
Most mails arrive > 3 business days.

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

(A) A large proportion of the mail that is correctly addressed is damaged in transit.
 Negation: 90% of the mail is incorrectly addressed -> So they arrive late.
10% are correctly addressed -> So they arrive in 2 days. If zero % of the correctly addressed mails are damaged, still the condition is satisfied.
So incorrect

(B) No incorrectly addressed mail arrives within two business days of being sent. ->  Cannot be inferred.

(C) Most mail that arrives within two business days of being sent is correctly addressed. -> looks ok.
 -> Damaged in Transit for correctly addressed mails will take > 2 days
-> Incorrectly addressed mails will take more than 2 days

(D) A large proportion of mail is incorrectly addressed.
 -> Incorrectly addressed mail can take > 2 days
-> Damaged mails can take > 2 days. 
How can one infer that which part is in majority -> Cannot be inferred.

(E) More mail arrives within two business days of being sent than arrives between two and three business days after being sent. ->  Cannot be inferred.

aditya8062 · Answer

why this interpretation is wrong and why C cannot be answer !!

the fact that  "Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent"  DOES NOT MEAN that  "Incorrectly addressed mails will take more than 2 days"  . if you are saying that  "Incorrectly addressed mails will take more than 2 days"   then that is something you are assuming . NO WHERE in the passage such statement is written and neither it can be inferred !!

why C is wrong

C says:    Most mail that arrives within two business days of being sent is correctly addressed. ------------->there might be a situation where  INCORRECTLY ADDRESSED  mail are  MOST  that arrives within 2 days !!

kinjiGC · Answer

Yes I agree it is not written but it is from well known outside knowledge as if the correctly addressed mails are able to reach their destination in 2 days, incorrectly addressed mails will take more time to reach because the mails will reach the incorrect address in 2 days.

simplyanuj · Answer

I think by POE the Answer should be D .Here's why i think so: A) A large proportion of the mail that is correctly addressed is damaged in transit. Incorrect Since we are not told anything specific about the amount of correct mail that is damaged in transit we cant infer this, if anything we can infer the opposite that this proportion should be small as the argument mentions that nearly all correct mails arrives within 2 days. B) No incorrectly addressed mail arrives within two business days of being sent. Incorrect since we are just told that nearly all correct mail arrives within 2 days while it is nowhere said whether incorrect can arrive in 2 days or not C) Most mail that arrives within two business days of being sent is correctly addressed. Incorrect it might be possible that that sometimes the proprtion of incorrect mail that arrives in 2 days might be more that correct mail. D) A large proportion of mail is incorrectly addressed.Correct 1)Since we are told that most mail arrives after 3 days so this can mean that either the proportion of incorrect is more or more correct mail is damaged in transit 2)we are also told that nearly all correct mail arrives in 2 days so from this can we infer that proportion of correct mail that is damaged in transit is very small so now combining statement 1 and 2 we can Infer that a large proportion of mail is infact incorrectly addressed. E) More mail arrives within two business days of being sent than arrives between two and three business days after being sent.Incorrect there is nothing given to compare the amount between 2 days and 2-3 days, we are just told that most mail arrives after 3 days. Thanks AK Please press Kudos if explanation makes some sense to you :-D

souvik101990 · Answer

miro · Answer

The key to this Qs is the first sentence: "Nearly all mail that is correctly addressed arrives at its destination within two business days". It can be inferred that the portion of 'correctly addressed mail that gets delayed is smaller'. Options A & Option D scenarios are therefore not equally feasible.

Besides, this is an LSAT question

akashjai · Answer

You just changed the mindset of the whole question with all these girls and love steaks....

However, when you look at Option D, we can say that Most of the mail gets damaged in Transit and arrive later than 3 days. It need not be Incorrectly Addressed.
Moreover, nowhere is it ever mentioned that Incorrectly mail cannot be delivered in 2 days. 
All that we know is that the Correctly Addressed mail reaches in 2 days.

souvik101990 · Answer

This is an LSAT question, and that response was from a Manhattan Prep LSAT user. I thought the comment was very insightful. You may like this one more.

Or this one

Nevernevergiveup · Answer

Here is my analysis

Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fact, correctly addressed mail takes longer than this only when it is damaged in transit. Overall, however, most mail arrives three business days or more after being sent.

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

A. A large proportion of the mail that is correctly addressed is damaged in transit........ .may or may not be. cannot be inferred.

B. No incorrectly addressed mail arrives within two business days of being sent...... we have no info regarding incorrectly addressed mails arrival.

E. More mail arrives within two business days of being sent than arrives between two and three business days after being sent........ cannot be inferred. new info

Now between options C and D

C. Most mail that arrives within two business days of being sent is correctly addressed.......... .this must be true as there is no other way it can be false.

D. A large proportion of mail is incorrectly addressed....... .since most mail arrive late the reasons may vary. A large portion of mail can be either incorrectly addressed or damages during transit. I feel we cannot infer the this statement as this is must be true question.

can someone please explain?

shasadou · Answer

Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fact, correctly addressed mail takes longer than this only when it is damaged in transit. Overall, however, most mail arrives three business days or more after being sent.

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

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

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

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

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

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

Source : LSAT PrepTest20 Q#19

Let us engage into the stem: correctly addressed mails get delivered in time - not argued. But why the overall delivery time is 3 days??? Where does it come from? Correctly addressed but damaged mails are delivered after days? Definitely! What about Incorrectly addressed mails? Do they get delivered within 2 days? Hm. May be some of them. What if one can incorrectly indicate the number of the house or index and the mail either will not be delivered at all or be delivered to wrong index from which it will have to be redirected after verification. It gonna take more than 2 days to be delivered than a healthy mail in healthy circumstances takes to get delivered.

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

A. A large proportion of the mail that is correctly addressed is damaged in transit.  I think this is the trickiest incorrect answer! Hell yeah! Many delivery delays happen due to damage. But does the stem conclusively says this or it is our conclusion? It will be our conclusion if we choose this tricky option. We love the idea that delay is caused by damage. But nowhere does the stem say that there are lot of damaged correctly addressed mails - we love to make this conclusion.

B. No incorrectly addressed mail arrives within two business days of being sent.  It means that ALL incorrectly addressed mail gets delivered with delay. Not necessarily. There can be just 1 mail that was delivered in 1 hour after submition - the stem allows that.

C. Most mail that arrives within two business days of being sent is correctly addressed. Again not necessarily. This statement reverses the cause-effect relationship in the arguement. The arguement says correctly addressed ---> be delivered in 2 days. Not vice versa. Hence is not necessarily true.

D. A large proportion of mail is incorrectly addressed.  What about incorrectly addresed mails which are not directly mentioned in the stem but which definitely are implied as opposed to the correctly addressed mails. Besides that the 3 days average defintely gets affected by this category of mails - incorrectly addressed - along with the damaged correct ones. As long as the stem does not guarantee that there a lot of damaged correct mails then the delays are caused by the another mail category: incorrectly addressed. really tricky

E. More mail arrives within two business days of being sent than arrives between two and three business days after being sent.  the stem does not tell anything about propotions.

Nearly all mail that is correctly addressed arrives at its destination

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Nearly all mail that is correctly addressed arrives at its destination

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