Logical Reasoning

PT21 · S2 · Q18 All of the cargo ships of the Blue

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All of the cargo ships of the Blue Star Line are over 100 meters long, and all of its passenger ships are under 100 meters long.

Statements

conditional (all - Left side, sufficient)

BSL cargo ship → over 100m BSL pass ship → under 100m GSL cargo ship → under 100m and post-1980 GSL pass ship → under 100m and post-1980

conditional (only - Right side, sufficient)

Use of PT's dockside → (BSL or GSL) and under 100m

quantifier (most)

Most BSL are pre-1980.

fact

S.S. Coral is cargo ship docked at PT.

Evaluate

We certainly wouldn't ever try to diagram this many conditionals on our page. There are just too many facts to take stock of. With conditionals, ultimately we care about whether we can chain them together with other conditionals or whether we can apply them to any provided facts.

The final sentence provides us with a fact that begs to be integrated with the previous information.

Given that the S.S. Coral is docked at Port Tropica, we know it belongs to BSL or GSL, and we know it must be less than 100m long.

Given that the S.S. Coral is a cargo ship, if it's BSL cargo then it's over 100m. If it's GSL cargo then it's under 100m.

So we know that the S.S. Coral would have to be a GSL cargo ship. Since all GSL cargo ships were built after 1980, we could also say that the S.S. Coral was built after 1980.

Goal

Look for anything provable, but it will probably reward us for deriving all the knowable facts about the S.S. Coral: - a GSL cargo ship, built after 1980

18.

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

Correct
The S.S. Coral was built
Why this is right
Since it's docked at PT, it's gotta be Blue or Gold Star line and it's gotta be under 100m. Thus, of the two options (Blue Star cargo or Gold Star cargo) it could only be a Gold Star cargo ship. And since it's a Gold Star cargo ship, we know it was built after 1980.
Skill tested: Must be True · how this choice captures the argument's function is the move to repeat next time.
80% picked this
The S.S. Coral belongs to
Contradicted
If the S.S. Coral was a cargo ship that belonged to BSL, it would be over 100 m long, which would mean that it is not eligible to use the dockside facilities of Port Tropica. But we know that it is using those facilities.
4% picked this
Port Tropica is served only
Unsupported
We know that PT is used only by the two lines and only for ships under 100 m long, but we were never told it only serves cargo ships. Both the Blue and Gold Star passenger ships are under 100 m long; they could presumably serve Port Tropica.
1% picked this
Port Tropica is not served
Unsupported
We know that PT is used only by the two lines and only for ships under 100 m long. Blue Star's cargo ships are too big for PT, because they're over 100 m long, but the Blue Star passenger ships are under 100 m long; they could presumably serve Port Tropica.
9% picked this
All of the ships of
Too Strong: all
We were never told that cargo and passenger ships are the only two types of ships. So it's possible that BSL and GSL have ships we didn't get any information about. However, even with the information we did get, we learned that most BSL ships were before 1980 and all GSL ships were after 1980. So we could say "most of BSL's cargo and passenger ships are older than any of the cargo and passenger ships of the GSL." But we can't say all of BSL's ships are older. Most of them were built before 1980, but leaves open the possibility that some of them were built last week.
6% picked this

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