Q6 - The Rienzi, a passenger ship

[peg_city]

Please explain to me why D is wrong.

We know
*Normally, when a ship sinks as rapidly as the rienzi did, water does not ever quickly enough for the ship to be fully flooded - IE it will implode
*The rienzi did not implode

D) if the rienzi had sunk more slowly, it would have imploded

why is this wrong

[ManhattanPrepLSAT1]

Good question! And thanks for bringing this one to the forum... Let me answer your question with one of my own. How do you know that of the Rienzi had sunk more slowly, it would not be fully-flooded?

Remember, ships that sink deep into the ocean when not fully-flooded will implod. But we don't know anything about whether they will implode when ships are fully-flooded. We do know that "normally, when a holed ship sinks as rapidly as the Rienzi did, water does not enter the ship quickly enough for the ship to be flooded." But answer choice (D) is discussing what would happen if the ship had not sunk at the "rapid" pace mentioned in the stimulus.

Does that answer your question?

[peg_city]

Yes, I get it. Thanks
I really should have got this question right

[jiyoonsim]

Could you explain why B) isn't the right answer, but C) is?

This was one of the most confusing questions I've ever seen. There are loads of unnecessary information!

[ManhattanPrepLSAT1]

Happy to!

This question asks us to find the answer choice that must be true based on the information presented in the stimulus. There are many claims made in the stimulus and it's up to us to figure out what can be inferred from them.

We know that if the Rienzi were not fully-flooded when it hit the ocean floor it would have imploded. We know that the ship did not implode and from these two claims we can infer that the ship was fully-flooded when it hit the ocean floor. We also know that normally water doesn't enter a ship quickly enough for this to happen, although it can if there is sabotage in involved.

Weaving all of these ideas together allows us to say that if sabotage was not involved, the Rienzi did sink unusually fast - expressed in answer choice (C).

Let's look at the incorrect choices now too.

(A) is out scope. We were not given information on the ship's construction. if this were an Explain a Result question this answer choice might be more appropriate. But does not represent something we know from the stated information.
(B) is contradicted. If the Rienzi would have hit the ocean floor while still not fully-flooded, it would have imploded. But it didn't implode.
(D) seems to run counter the stimulus as well. We know that if the ship were not fully-flooded when it hit the ocean floor it would implode. if the ship had sunk more slowly, then it would likely be fully-flooded when it hit the ocean floor - a situation about which we are not provided information on.
(E) may be true, and might help explain the situation similar to answer choice (A) but cannot be inferred from the information provided.

Hope that helps, and let me know if that doesn't answer your question!

[eve.lederman]

Basically this entire question hinges on the word "normally?"

My thinking:

Rapid sinking -> water doesn't enter rapidly enough for FF.
(so, rapid sinking -> no FF)

no FF-> implode
- - - -
We know the ship didn't implode, so looking at a chain, I inferred that there was no rapid sinking.
I eliminated D because it was reversed and so i was left with C, but I'm still not content with C.

[christine.defenbaugh]

Thanks for asking, eve.lederman!

The word 'normally' is pretty darn important, here, it's true - it's absolutely critical to realize that you're not dealing with a strict conditional when they say that 'rapid sinking --> not full flooding'. That's what normally happens, but that leaves open the possibility of abnormal events (including, but not limited to, sabotage). This is emphasized not just by the use of the word 'normally', but also by the fact that in the very next sentence, we find out that full flooding can be achieved by sabotage.

Now, the next connection IS a strict conditional: if there's no full flooding in deep sinking, that ship will implode. Since the Rienzi didn't implode, we can absolutely follow the contrapositive of the strict conditional to conclude that the Rienzi must have had full flooding.

But we can't follow the contrapositive of the first connection, because it isn't a strict conditional. Not only that, when you try to, you end up concluding that the Reinzi didn't sink rapidly - but we know that it did! By concluding that the Reinzi didn't sink rapidly, you are contradicting information in the stimulus!

Instead, we must accept 1) that the Rienzi sank rapidly and 2) that the Rienzi had full flooding. And since normally those two things don't happen together, that means something weird had to have happened: either it flooded faster than "normal", or sabotage!

Always watch out for statements that appear to be conditionals but are not 100% guarantees, and never infer something that directly contradicts information you've already been given!

Please let me know if that helps clear up a few things!

[roflcoptersoisoi]

The key to getting this question right is being able to draw an inference from the last and second last sentences which are conditional statements and relating them back to the other parts of the stimulus.

The second last and last sentences can be mapped out as so:

S= Sink deep into ocean.
FF= Fully flooded.
I = Implode.

Second last sentence: S + ~FF ---> I
Last sentence : ~I

Therefore we can make the valid inference that: ~I ---> ~S or FF (note this is simply the contrapositive of the second last sentence).

Now we know from the first sentence that the ship sank, so it must be true that the ship was FF when it reached the ocean floor. We also know that a ship can be fully flooded if it is sabotaged and that normally when a ship sinks at the rate at which the Rienzi did, water does not enter the ship quickly enough to completely flood it when it reaches the ocean floor.

Since we know Renzi was FF flooded we can conclude that it was either sabotaged or the rate at which water entered the ship was not "normal", i.e, the rate at which it entered was unusual an anomaly.

(A) Nope, we're given no info as to how the Rienzi was constructed, get rid of this.
(B) This cannot be true. This would be the correct answer if the question stem we're switched to MUST be false/ Could be true EXCEPT. We're told that it did not implode, therefore it must have been fully flooded by the time it reached the ocean floor.
In logical language this answer choice is saying : ~FF and we know that if ~FF --> I. However, we're told that ~I, therefore we can conclude that ~ I --> ~S or FF, so it would have been necessary for FF to have occurred.
(C) Bingo. We already know that since the ship imploded it was fully flooded when it reached the ocean floor. Since it was fully flooded when it reached the ocean floor, the ship could have either been sabotaged or water could have entered it at an unusual rate. This answer choice eliminates the former as a possibility, we're left to conclude that the latter must have occurred.
(D) This could be true, but need not be true given the information we're given in the stimulus. We're only told that the ship sank at X rate and didn't implode. Perhaps is it sank at a rate 1/5 or 1/10 of X it would have imploded, but we cannot say for certain because that info is not provided to us in the stimulus, how slow would the Rienzi be sinking, what exactly is the correlation between rate of sinking and imploding ? Remember we want not to infer based on our prejudices or info that's not situated in the stimulus. Your thinking needs parochial and abstract when it comes inference questions.
(E) Again like A we're given no info as to how the ship was constructed.