Flawed Parallel Reasoning Questions - - Question 4

The Scorpio Miser with its special high-efficiency engine costs more to buy than the standard Scorpio sports car. At ...

Dsh August 29, 2024

I dont get why this answer is correct

The answer mentions the machine, the Roadmaker, to be more advantageous showing a certain preference for one over the other that was not present in the passage. The passage mentioned that it would be less to make up the difference if prices were lower but did not show any preference for one over the other as the answer choice does. I did not select this answer as correct because it showed a preference that was not apparent in the passage. Why is it still right despite making a suggestion at the end.

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Emil-Kunkin August 30, 2024

Let's look at the passage, because what we really care about here is the flaw.

The passage tells us that an option is more expensive upfront, but saves on costs when in operation when compared to a cheaper option. That is, one is cheaper to buy but more expensive to run, and the other is more expensive to buy but cheaper to run. The passage then determines that when the cost of running decreases, this favors the one that was more expensive to buy but cheaper to run.

This is wrong however. If it becomes cheaper to run because gas prices decreased, than it is actually better to buy the option that is more expensive to buy but cheaper to run. Imagine that option 1 costs 10, and requires 2 gallons per day, and option 2 costs 20 but only requires 1 gallon a day. If a gallon costs 1, then after 10 days, the options are even, and after more than ten days option 2 is actually better.
However if the price falls to .5 per gallon, then it takes 20 days for the options to be even, and option 2 is only better than option 1 on the 21st day. This is the opposite of what the passage says.

C is correct because it makes the exact same mistake. It tells us that when the running cost is cheaper this works in favor the option that is cheaper to run, when in reality the opposite is true.

While the phrasing of c is slightly stronger than the passage they convey the same idea. If the break even point is lower for the Miser, then we inherently would prefer the miser if we will go over that break even point. Given that this is just a cost and profit question this is absolutely a preference.