A certain auto repair shop services a particular make of car in the

Hi Harley

A quick Q with this one.

I opted option C, which is the incorrect option.

The concusion of the argument is ' Training helped mechanics to do their job better'.

Option D says: this year they had 35% more cars and only fewer than 2% were not successful. This clearly means that mechanics are doing a great job.

Please could you hightlight my mistake.

Hi,

C cant be the correct answer because the training was given over a year ago and if the bulk of mechanics joined after that then the training is not responsible for the improvement. So it weakens the argument.

As per D, the number of cars served has increased while the unsuccessful repair rate has dropped. Hence D.

Regards,
Dom.

2% of 135 is only 2.7 or roughly 3 cars

I disagree with the question being in verbal section

Can you pls explain how choice D is the correct answer?

Thanks

let's do some maths
Given X as a number of car repaired by this shop 3 years ago.
hence,the number of unsuccessfully repaired cars is 0.04X

From D,
The total number of car repaired by this shop is 1.35X
hence,the number of unsuccessfully repaired cars is 1.35*0.02X ---> 0.027X
Thus,whatsoever the value of X is,the number of unsuccessfully repaired cars is fewer today.

Sleepynut's explanation is correct, but if it makes anybody feel better: don't worry, you'll never have to do math in an official GMAT verbal question.
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Official Explanation Magoosh:

This is an EXCEPT question. Four of the answers will be legitimate weakeners, and those will not be correct. One statement either will strengthen the argument or will be irrelevant, and this odd one will be the correct answer.

The credited answer is (D). The percentage of un-repairable cars dropped from 4% to 2%: it was cut in half. A true weakener would be if the number more than doubled --- then the rise in total number of cars would offset the change in percent, and the total number of un-repairable cars would increase. Here, though, an increase of 35% is far less than doubling, so this doesn't offset the drop in percent. This is not a valid weakener, so it is the correct answer.

If statewide smog regulations removed older cars from the road, then there would be fewer old un-repairable cars, and the decline would not be due to the skill of the mechanics. Choice (A) is a true weakener, so it is not correct.

If the manufacturer had a recall of models with a serious engine flaw, that would also reduce the number of un-repairable cars, and again, the decline would not be due to the skill of the mechanics. Choice (B) is a true weakener, so it is not correct.

If most of the mechanics were hired in the past nine months, they would not have received the mechanics training course, given over a year ago, so whatever success they have could not be attributed to this course. Choice (C) is a true weakener, so it is not correct.

Older cars are more likely to have un-repairable problems. If the new shop handles all the older cars, then they would wind up with more of the un-repairable cars, and the repair shop in question would have fewer of these cars. If this shop sees more newer cars and fewer older cars, then fewer of the cars overall will be un-repairable. The decline would not be due to the skill of the mechanics. Choice (E) is a true weakener, so it is not correct.

The total number of cars served per year by this shop has increased by 35% over the past three years.
D strengthen the argument, if number of increase and percentage of failure decrease from 4% to 2% then it means efficiency of repair has improved.

Type: Find the answer choice that DOES NOT WEAKEN the conclusion.

Conclusion: Training course (introduced one year ago)---->Increased skill of mechanics---> fewer cars beyond the mechanics' capability to repair such cars.

A) Three years ago, statewide smog regulations had the effect of removing the oldest and most unreliable vehicles from the road. - (A) gives us an alternate explanation for the observed results: the drop in the % of unsuccessful repairs was due to a decrease in the number of such cars available for repair in the first place. Hence, (A) weakens the conclusion.
B) The manufacturer of this particular make of car recalled a few models due to defects that potentially jeopardized the engine. - (B) gives us an alternate explanation for the observed results: the drop in the % of unsuccessful repairs was due to a decrease in the number of such cars available for repair in the first place. Hence, (B) weakens the conclusion.
C) More than half of the mechanics have been hired in the past nine months. - the training course was introduced a year ago. But if more than half of the mechanics who currently work in this shop have been hired in the past 9 months, there is no way for them to improve/gain knowledge from this course that was offered a year ago. Hence, (C) weakens the conclusion.
D) The total number of cars served per year by this shop has increased by 35% over the past three years. - this actually supports the conclusion since we can infer from (D) that despite a steady increase in the number of cars served, the overall percentage of unsuccessful repairs dropped to 2%. This would imply that mechanics who worked on these cars were indeed skilled. Hence, (D) does not weaken the conclusion. Therefore, (D) is the right answer choice.
E) A new shop uptown specializes in repairing cars of this make more than six years old, and most of these older cars are taken to this shop. - (E) gives us an alternate explanation for the observed results: the drop in the % of unsuccessful repairs was due to a decrease in the number of such cars available (to this particular shop) for repair in the first place. Hence, (E) weakens the conclusion.

Option C leaves room for scope.

More than half mean, it could be 51 % staff replaced, 90 % of staff replaced or 100% staff replaced. That's why I had eliminated the option.

If three years ago the older cars were already removed, how is it possible that the rate goes down. The rate of three years ago already incorporated this event. I think A doesn't work

VeritasKarishma AndrewN

Hello, MPRS22. I keep writing this in the forum, but people persist: stick to official, GMAC™-created questions for Verbal practice. I can assure you that if you master this somewhat narrower pool of questions, you will be primed to ace the Verbal section, even if your performance on third-party questions is so-so. I do not think the logic in this question is airtight, and I do not think it would appear as such on the GMAT™.

- Andrew
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I would think the question as written is fine but I don't agree with the explanation.

3 yrs ago, 4% of all repairs were found to be unsuccessful.
So say today is 31st Dec 2021. So on 31st Dec 2018, we found that 4% repairs were unsuccessful in 2018.

This year, only 2% repairs were unsuccessful. So in 2021, only 2% were unsuccessful.

So the mechanics course given in Dec 2020 seems to have worked.
It increased the skill of mechanics at this particular shop, so that fewer cars are beyond their ability to repair (out of all the cars out there, not just the ones brought to them).

When I say that this Math course has improved my ability to solve problems such that fewer problems are beyond my reach now, it means of the total problems our there, fewer are out of my reach.
So perhaps out of every 100 problems I solved before, I couldn't solve 10 before and now out of every 100, I am unable to solve 5.
How many problems I was actually given to solve in the two cases is irrelevant (as long as both samples were indicative of population).

That is what I take away from the argument and if that is not what it meant, then I have no explanation for it.

A) Three years ago, statewide smog regulations had the effect of removing the oldest and most unreliable vehicles from the road.

So on 31st Dec 2018, regulations removed the worst cars. That could explain the lower number of 2% and the training may have nothing to do with it. Weakens the conclusion.


B) The manufacturer of this particular make of car recalled a few models due to defects that potentially jeopardized the engine.

Some defective vehicles were recalled. That could explain the lower number of 2% and the training may have nothing to do with it. Weakens the conclusion.

C) More than half of the mechanics have been hired in the past nine months.

The training happened a year ago but most mechanics are new. The reason for improved numbers may not be the training then. Weakens.

D) The total number of cars served per year by this shop has increased by 35% over the past three years.

Number of cars served per year has increased over the 3 yrs. It doesn't do anything to the conclusion. I would not say that it weakens the conclusion even if this number were 300%.

E) A new shop uptown specializes in repairing cars of this make more than six years old, and most of these older cars are taken to this shop.

Since older cars are taken to the new shop, it may be the reason for the decrease. Weakens the conclusion.

Answer (D)
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