#11 - In 1990 major engine repairs were performed on 10

[Administrator]

Complete Question Explanation

Resolve the Paradox-#%. The correct answer choice is (C)

Here we have a resolve the paradox question whose answer may be quite conducive to prephrasing: National Motor Company shows 10% of its cars from the 1970’s requiring major work, but only 5% of its cars from the 1960’s requiring work, despite the fact that we would expect the older cars to require more major repairs. So why would there be fewer cars from the 1960’s in need of major repairs? Perhaps there are less of those older cars on the road in general. Correct answer choice (C) provides for this exact possibility: the older a car, the less likely it will remain running and in good repair.

[niketown3000]

Hello,

You guys are so helpful! I wanted to find out why D is wrong.

I recently asked a question about prephrasing that I had when I finished the virtual course. I tried Jon Denning's excercise, but I was unsure why my prephrase was weak and choice was wrong here.

Prephrase: Something happened in the way cars were developed between 1960 - 1970 that made more repairs for 1970's cars.

Way I read D: The simplified 1970 engines could have been the things that cause more problems and therefore more repairs for 1970s cars than 1960s. Am I read/supposing too much?

[Jon Denning]

Let me say a brief bit about prephrasing for questions like this (Resolve): your prephrase is typically not going to be all that precise with respect to exactly what the correct answer will say. That is, for a Resolve question it's often going to be pretty impossible to predict exactly what will resolve the paradox, so instead focus on what the paradox is and the specific information you're given about it. That should be sufficient to let you better evaluate what the answers say when you start reading them.

Here, the paradox is that 10% of cars built in the 70s needed major repairs, whereas only 5% of cars built in the 60s needed major repairs. That's odd because you'd expect the older cars to require more repairs than newer cars, yet the statistics seem to indicate the opposite.

(C) does that nicely by telling us that older cars are more likely to be discarded than repaired, so 60s cars that needed repairs wouldn't be repaired as often as 70s cars that need repairs. That explains the odd numbers in the stimulus.

(D) fails for a few reasons. One, it doesn't explain why the 70s cars appeared to need MORE repairs than those from the 60s. If anything it would make it seem like 70s cars would need fewer repairs due to the simplified engine. Secondly, it's wrong of us to assume that a less complicated engine would necessarily translate into needing fewer (or more) repairs. We simply can't know that, so this answer is irrelevant to the specifics of the paradox.

Remember, a prephrase is crucial, but on questions like this where a specific prediction fails you must instead focus on the question type and the nature of what the correct answer must DO.

I hope that helps!

[helloiameric]

Hi,

Thanks for all the help. What I don't understand is, since it says "still registered," and it would seem that any car which is "scrapped" would not still be registered, C cannot be the correct answer because it would just effect the overall number of cars still on the road, not the percentage that received engine repairs.

Let's say we have 30 cars from 1970, and 30 from 1960.

1970 1960
30 30
Then a certain amount of cars (more from 1960) are scrapped (I'm assuming this means taken off the road and therefore not registered)
-10 -15
leaving
20 15

Yet the percentage of cars which receive engine repairs would still remain the same (10% and 5%), irrespective of the number of cars "still registered."

Can you help me to understand this discrepancy?

[Ron Gore]

Great question! The term appears to refer to having a car registered with the government for use on the roads. The issue you point to is that if a car is scrapped, then it would not be on the road. If it is not on the road, then it would not be registered. However, there is a timing issue here that you may not be considering.

Let's say that on January 1, 1990, there are a certain number of 1960s era cars on the roads, still registered. During the year, a certain percentage of those cars needed major engine repair. Answer choice (C) says that, because these cars are older, their owners are less likely to repair them than are the owners of the 1970s era cars to undertake similar repairs. Instead, a greater percentage of the 1960s era cars will be scrapped at some point during the year. So, although the 1960s cars were on the road and registered at some point in 1990, they were more likely to be scrapped than repaired when the need arose at some later point in the year.

Please let me know if that helps.

Ron