Last year all refuse collected by Shelbyville city services was incine

Thanks for the question imSKR! It seems like a lot of people are unsure about why D is a better answer than A, so let's look at both:

(A) This year, no materials that city services could separate for recycling will be incinerated.

Okay, I see why this sounds like a good answer. If recycling is not incinerated, then there will be less ash put into the air. That makes sense. However, we don't know for sure that recycling makes up HALF of all refuse picked up in the city. We just know there is enough of it to reduce the number of refuse truck pickups by half. For all we know, these trucks may end up picking up MORE refuse per load than they used to because they have to cover for the reduced number of available trucks. How much trash ends up in each of those truck loads is not mentioned at all here. Will these trucks pick up 50% less stuff overall if you take out recycling? We don't know. Therefore - this isn't the best option.

(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.

This is a much better choice! For this system to work, each truck MUST NOT generate any more burnable trash than last year to get to the 50% goal:

If 50% fewer trucks each pick up the SAME AMOUNT per load that they did last year, then they will meet their goal.
If 50% fewer trucks each pick up MORE per load than they did last year, then they will not meet their goal.


We hope this helps!

Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

P: Last year all of the refuse collected was incinerated which led to a large quantity of ash
P: Shelbyville revamped its collection program to reduce the ash to half of last year’s total
C: Shelbyville will separate for recycling enough refuse to reduce the # of truckloads to be incinerated to half

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.

Argument still works…we can still see a reduction in the number of truckloads of refuse to be incinerated.

(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.

No. This presumably strengthens the argument, but the passage won’t break even if this were not true. We don’t have any specific details about the city’s financial capacity.

(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.

No. The key here is to focus on the word proportion. It’s really not clear which way this choice takes us. For example, you could have a larger proportion of recyclables and yet the absolute amount of refuse collected could be higher. On the other hand, you could have a larger proportion of recyclables and less refuse.

(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.

Correct. Negating this reveals something that would destroy the argument all together. The goal of the revamped collection program is to reduce the quantity of residual ash. If it turns out that their program actually leads to the production of more residual ash, then there’s no reason to think that this year’s total will be half than that of last year’s.

(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

I wasn’t particularly sure what to make of this, my thinking was that if the total amount of refuse increased irrespective of the fact that the number of trucks is cut in half, then shouldn’t the total amount of ash increase?

GMATNinja What do you think about my reasoning for E?

AnishPassi GMATNinja @veritaskarishma

Hi-

I know why D is the correct answer.

However, i am not sure abt why A is the wrong answer.

If some recyclable material is incinerated, and number of truckloads are reduced to half (to reduce ash generated to half of last years ash) then ash generated would me more! In that case- this is required right?

The way I eliminated it was that- Option D did a better job in weakening the option. But want to understand, why exacltly this option is wrong based on my thought process. Thanks

Hi Shantanu,

I think I see what you did there.

Total ash = Ash generated by the refuse in half the trucks + ash generated by the recyclable material that is actually incinerated
Thus total ash generated > 50% of last year's.

Did I get you correctly?

If so, what you fail to see is that even if some recyclable materials are separated for incineration, they'd be a part of the truckloads that are to be burned, and not in addition to the truckloads.

Basically, is it necessary that half the refuse that is to be incinerated consists entirely of non-recyclable materials? Can't they burn some recyclable material and still maintain this year's amount of ash to within half of last year's? As long as the total ash generated is half of last year, we're good. Even if some of that ash is generated by recyclable materials. That's why this statement is not necessary.

Does that make sense?

I'm a big fan of the "Tweet" approach to summarizing arguments: 140 characters or fewer! I've found that the majority of times some sort of long story is required, things don't turn out well!

Conclusion:
Cut ash in half.

Premises:
Separating recycling will cut trucks for incineration by 50%

So the plan as a whole goes:
Separating recycling will cut trucks for incineration by 50% --> Cut ash in half

Let's look at the answer choices:
(A) This year, no materials that city services could separate for recycling will be incinerated.
We are told a fact that doing the recycling thing will cut the trucks for incineration by half. Eliminate.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
The plan doesn't mention whether cost matters; the plan is just to reduce ash by 50%. Eliminate.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
That might be nice, but we have no idea whether it will be 50%. Eliminate.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
Ah, we cut the number of truckloads by half, but without this answer choice, we could still end up with more than 50% of the ash we had previously. Love it.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.
We are told that we're going to cut the number of incinerated truckloads by 50%. It doesn't matter how much total refuse there is. Incinerated truckloads is still half of last year. Eliminate.

Answer choice C.

I chose last line as conclusion :'This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.'

and then chose C] to strengthen the above conclusion.

how do I identify whether the 'truckloads will be reduced to half' is a premise or a conclusion?

Hi Experts, GMATNinja , egmat , CrackverbalGMAT

I have understand that why Option D is the assumption. But I have one query, Why we have ignored the possibility that the amount of refuse collected can be increased this year. Hence, option D wont have a impact. In-fact the truckload of the residual ash will increase. Are me assuming that the collected refuse are being constant in both years.

I wanna know where why thought process is missing anything.

Thanks in Advance.

Notice that goal is the following:

to reduce the amount of residual ash

So, the result that matters is the reduction in the amount of residual ash. Thus, only the refuse that will be incinerated matters because only the refuse that will be incinerated will contribute the creation of residual ash.

The city has the following plan:

reduce the number of truckloads of refuse to be incinerated

So, as you said, it's possible that the total amount of refuse collected will increase. However, the number of truckloads of refuse TO BE INCINERATED will be reduced. Thus, we can be sure that the RELEVANT number of truckload will decrease.

Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Analysis:
Outcome - This year, Shelbyville wants to generate half of last year's ash generated by burning waste
Plan - The number of truckloads that Shebyville will burn this year will be half of what it burnt the last year

Which of the following is required for the revamped collection program to achieve its aim?

We need to find the assumption!

Note - In questions where we are given a plan and an outcome, the author could assume one of the following:
1. The plan will necessarily work and result in the outcome
2. There is no alternative to the proposed plan

(A) This year, no materials that city services could separate for recycling will be incinerated.
"This year" triggers that the comparison is made with some other period. However, we are not given the other side of the balance to compare anything

(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
The argument doesn't speak about the cost. Therefore, this does not apply

(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
Negation: Refuse this year will contain the same or lesser proportion of recyclable materials than last year.
Analysis: Even if the negation is true, it does not attack the plan. The plan says that we will burn half of last year's truckload of waste. Let's say, last year there were 100 truckloads of waste (recyclable + non-recyclable). This year, they will burn 50 truckloads (recyclable + non-recyclable). We don't know and are not concerned by the proportion of recyclable and non-recyclable refuse

(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
Negation: The burnt waste will produce more ash per truckload this year than last year
ANalysis: If that is the case, then by burning the same truckloads of waste this year will generate more ash than last year. It attacks the plan.

(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.
Negation: The amount of refuse collected by greater than last year
Analysis: Even if the amount of refuse collected is 1000x, the plan is to burn half of what Shelbyville burnt last year.

Therefore, (D) is the answer.