Logical Reasoning

PT154 · S4 · Q25 The technical sophistication of commercial

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The technical sophistication of commercial fishing equipment increased steadily from 1960 through 2010, which enabled the commercial fishing industry to harvest a greater percentage of the total amount of fish, by weight, in the world’s oceans in each succeeding year during that time.

Statements

From 1960 to 2010, the fishing industry was able to harvest a greater percentage of the total amount of fish, by weight, in the world's oceans, in each succeeding year.

The harvest, by weight, increased steadily from 1960 to 1995, but didn't increase after 1995.

Evaluate

We usually read Must Be True looking for Conditional, Causal, or Math-y type ideas. This one seems to giving us Math-y ideas, so reconciling the first and second sentences will give us some mathematical inference.

We know that the fishing industry caught a higher percentage of the weight of the fish in the ocean each year.

Let's pretend there are 1,000 tons of fish in the ocean each year.

% caught tons caught 1960 10% 100 1965 11% 110 1970 12% 120 .... 1995 20% 200 2000 25% 200 2005 50% 200

We complied with two different constraints there: 1. percentage keeps increasing from 1960 to 2010 2. overall weight of fish caught increases from 1960 to 1995 3. overall weight of fish caught stops increasing from 1995 to 2010

But notice something funky with our numbers. For a while they kept equaling 1000 tons of fish in the sea, but once the percentage goes up and the tonnage caught stays the same, it means that the total weight of fish in the sea has to start decreasing.

% caught tons caught total in sea 1960 10% 100 1000 1965 11% 110 1000 1970 12% 120 1000 .... 1995 20% 200 1000 2000 25% 200 800 2005 50% 200 400

The inference they're going for here is the same as this: my rent has stayed the same for the past 10 years, but nowadays my rent is a bigger percentage of my income.

What can we infer? My income is lower now than it used to be.

If I'm paying a higher tax rate this year than last year, but the government is still getting the same money from me, then that means my taxable income has gone down.

Goal

We don't know for sure what's going on from 1960 through 1995. It's possible that the overall weight of fish in the ocean goes down, stays the same, or goes up.

But once we get to 1995, we know for sure that the total weight of fish in the ocean starts going down, because the % of available fish weight being caught keeps rising but the actual weight of fish being caught does not increase.

25.

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

After 1995, the number of
Out of Scope: number of fish
Nothing in this paragraph discusses number of fish at all, just weight, so we can't derive anything about number of fish.
27% picked this
After 2010, improvements in commercial
Out of Scope: beyond 2010
We don't have any information about anything after 2010, other than that the fishing industry's harvest by weight did not increase. It's still quite possible that the % of available fish kept increasing. Just because the first sentence has a cutoff date doesn't mean that after that date things changed. I can say "From 1960 to 2010, humans lived on Earth". That's a true statement and it does not logically imply that "after 2010, humans did not live on Earth".
10% picked this
Correct
The total amount of fish,
Why this is right
This was our prediction. Since the fishing industry is catching a higher % of the available fish each year, but the amount they're catching is not going up, that means that the total available fish is going down.
Skill tested: Must be True · how this choice captures the argument's function is the move to repeat next time.
56% picked this
The commercial fishing industry’s harvest,
Too Strong: significantly lower
We were told that the harvest weight did not increase from 1995 to 2010; but this is saying that the weight was significantly lower. We can't go from didn't increase to got much lower.
6% picked this
No significant improvements in commercial
Out of Scope: before 1960
Similar to (B), we don't know anything about what happened prior to 1960. Just because technological sophistication of fishing equipment increased from 1960 to 2010 doesn't mean that this time period was the first time there had ever been a significant improvement in fishing equipment.
2% picked this

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